diff --git a/backend/__tests__/routes/passwordStrengthDos.test.js b/backend/__tests__/routes/passwordStrengthDos.test.js
index 7e60320d..ab568497 100644
--- a/backend/__tests__/routes/passwordStrengthDos.test.js
+++ b/backend/__tests__/routes/passwordStrengthDos.test.js
@@ -65,8 +65,10 @@ describe('password validation length cap (zxcvbn DoS)', () => {
 
     // No route may hand errors.array() straight to the response.
     expect(src).not.toMatch(/errors:\s*errors\.array\(\)/);
-    // ...and the helper that replaces it must drop `value`.
-    expect(src).toMatch(/safeValidationErrors\s*=\s*\(errors\)\s*=>\s*errors\.array\(\)\.map\(\(\{ value, \.\.\.rest \}\)/);
+    // ...and the shared helper that replaces it must drop `value`.
+    const helper = require('fs').readFileSync(
+      require('path').join(__dirname, '../../src/utils/routeHelpers.js'), 'utf8');
+    expect(helper).toMatch(/safeValidationErrors\s*=\s*\(errors\)\s*=>\s*errors\.array\(\)\.map\(\(\{ value, \.\.\.rest \}\)/);
   });
 
   it('applies the cap through the context wrapper too', async () => {
diff --git a/backend/src/routes/adminApiTokens.js b/backend/src/routes/adminApiTokens.js
index eb56f0af..e81403e7 100644
--- a/backend/src/routes/adminApiTokens.js
+++ b/backend/src/routes/adminApiTokens.js
@@ -7,6 +7,7 @@
 
 const express = require('express');
 const { body, validationResult } = require('express-validator');
+const { safeValidationErrors } = require('../utils/routeHelpers');
 const { db, logActivity } = require('../database/db');
 const { adminAuth } = require('./../middleware/auth');
 const { requirePermission } = require('./../middleware/permissions');
@@ -65,7 +66,7 @@ router.post(
     try {
       const errors = validationResult(req);
       if (!errors.isEmpty()) {
-        return res.status(400).json({ errors: errors.array() });
+        return res.status(400).json({ errors: safeValidationErrors(errors) });
       }
       const { name, scopes, expires_at } = req.body;
       const { plaintext, hashed, preview } = generateApiToken();
diff --git a/backend/src/routes/adminCMS.js b/backend/src/routes/adminCMS.js
index db4bcc9f..0df5902b 100644
--- a/backend/src/routes/adminCMS.js
+++ b/backend/src/routes/adminCMS.js
@@ -3,6 +3,7 @@ const path = require('path');
 const fs = require('fs').promises;
 const multer = require('multer');
 const { body, validationResult } = require('express-validator');
+const { safeValidationErrors } = require('../utils/routeHelpers');
 const { db, logActivity } = require('../database/db');
 const { adminAuth } = require('../middleware/auth');
 const { requirePermission } = require('../middleware/permissions');
@@ -80,7 +81,7 @@ router.put('/pages/:slug', adminAuth, requirePermission('cms.edit'), [
   try {
     const errors = validationResult(req);
     if (!errors.isEmpty()) {
-      return res.status(400).json({ errors: errors.array() });
+      return res.status(400).json({ errors: safeValidationErrors(errors) });
     }
 
     const { slug } = req.params;
diff --git a/backend/src/routes/adminCategories.js b/backend/src/routes/adminCategories.js
index 9e6345df..8f81d4c5 100644
--- a/backend/src/routes/adminCategories.js
+++ b/backend/src/routes/adminCategories.js
@@ -1,5 +1,6 @@
 const express = require('express');
 const { body, validationResult } = require('express-validator');
+const { safeValidationErrors } = require('../utils/routeHelpers');
 const { db, logActivity } = require('../database/db');
 const { formatBoolean } = require('../utils/dbCompat');
 const { adminAuth } = require('../middleware/auth');
@@ -51,7 +52,7 @@ router.post('/', adminAuth, requirePermission('settings.edit'), [
   try {
     const errors = validationResult(req);
     if (!errors.isEmpty()) {
-      return res.status(400).json({ errors: errors.array() });
+      return res.status(400).json({ errors: safeValidationErrors(errors) });
     }
     
     const { name, slug, is_global = true, event_id = null } = req.body;
@@ -119,7 +120,7 @@ router.put('/:id', adminAuth, requirePermission('settings.edit'), [
   try {
     const errors = validationResult(req);
     if (!errors.isEmpty()) {
-      return res.status(400).json({ errors: errors.array() });
+      return res.status(400).json({ errors: safeValidationErrors(errors) });
     }
 
     const { id } = req.params;
@@ -191,7 +192,7 @@ router.put('/:id/hero', adminAuth, requirePermission('settings.edit'), [
   try {
     const errors = validationResult(req);
     if (!errors.isEmpty()) {
-      return res.status(400).json({ errors: errors.array() });
+      return res.status(400).json({ errors: safeValidationErrors(errors) });
     }
 
     const { id } = req.params;
diff --git a/backend/src/routes/adminCssTemplates.js b/backend/src/routes/adminCssTemplates.js
index 4bb4b288..3909f4fc 100644
--- a/backend/src/routes/adminCssTemplates.js
+++ b/backend/src/routes/adminCssTemplates.js
@@ -6,6 +6,7 @@
 const express = require('express');
 const router = express.Router();
 const { body, param, validationResult } = require('express-validator');
+const { safeValidationErrors } = require('../utils/routeHelpers');
 const { db, withRetry } = require('../database/db');
 const { adminAuth } = require('../middleware/auth');
 const { requirePermission } = require('../middleware/permissions');
@@ -58,7 +59,7 @@ router.get('/:slotNumber', adminAuth, requirePermission('branding.view'), [
   try {
     const errors = validationResult(req);
     if (!errors.isEmpty()) {
-      return res.status(400).json({ errors: errors.array() });
+      return res.status(400).json({ errors: safeValidationErrors(errors) });
     }
 
     const { slotNumber } = req.params;
@@ -92,7 +93,7 @@ router.put('/:slotNumber', adminAuth, requirePermission('branding.edit'), [
   try {
     const errors = validationResult(req);
     if (!errors.isEmpty()) {
-      return res.status(400).json({ errors: errors.array() });
+      return res.status(400).json({ errors: safeValidationErrors(errors) });
     }
 
     const { slotNumber } = req.params;
@@ -166,7 +167,7 @@ router.post('/:slotNumber/reset', adminAuth, requirePermission('branding.edit'),
   try {
     const errors = validationResult(req);
     if (!errors.isEmpty()) {
-      return res.status(400).json({ errors: errors.array() });
+      return res.status(400).json({ errors: safeValidationErrors(errors) });
     }
 
     await withRetry(() =>
diff --git a/backend/src/routes/adminEmail.js b/backend/src/routes/adminEmail.js
index 2a12ea7e..67d2c15d 100644
--- a/backend/src/routes/adminEmail.js
+++ b/backend/src/routes/adminEmail.js
@@ -9,7 +9,7 @@ const { requirePermission } = require('../middleware/permissions');
 const { requireFeatureFlag } = require('../middleware/requireFeatureFlag');
 const messagingGate = requireFeatureFlag('messaging');
 const { wrapEmailHtml, processEmailQueue } = require('../services/emailProcessor');
-const { errorResponse } = require('../utils/routeHelpers');
+const { errorResponse, safeValidationErrors } = require('../utils/routeHelpers');
 const logger = require('../utils/logger');
 const router = express.Router();
 
@@ -52,7 +52,7 @@ router.post('/config', [
   try {
     const errors = validationResult(req);
     if (!errors.isEmpty()) {
-      return res.status(400).json({ errors: errors.array() });
+      return res.status(400).json({ errors: safeValidationErrors(errors) });
     }
 
     const {
@@ -152,7 +152,7 @@ router.post('/incoming-config', [
 ], async (req, res) => {
   try {
     const errors = validationResult(req);
-    if (!errors.isEmpty()) return res.status(400).json({ errors: errors.array() });
+    if (!errors.isEmpty()) return res.status(400).json({ errors: safeValidationErrors(errors) });
     const { imap_host, imap_port, imap_secure, imap_user, imap_pass, imap_folder } = req.body;
     const { isHostAllowed } = require('../utils/networkValidation');
     if (!(await isHostAllowed(imap_host))) {
@@ -635,7 +635,7 @@ router.get('/queue', adminAuth, requirePermission('email.view'), [
   try {
     const errors = validationResult(req);
     if (!errors.isEmpty()) {
-      return res.status(400).json({ errors: errors.array() });
+      return res.status(400).json({ errors: safeValidationErrors(errors) });
     }
 
     const page = req.query.page ? parseInt(req.query.page, 10) : 1;
diff --git a/backend/src/routes/adminEventRename.js b/backend/src/routes/adminEventRename.js
index 8acdbcf0..bc1089ba 100644
--- a/backend/src/routes/adminEventRename.js
+++ b/backend/src/routes/adminEventRename.js
@@ -5,6 +5,7 @@
 
 const express = require('express');
 const { body, validationResult } = require('express-validator');
+const { safeValidationErrors } = require('../utils/routeHelpers');
 const { adminAuth } = require('../middleware/auth');
 const { requirePermission } = require('../middleware/permissions');
 const { requireEventOwnership } = require('../middleware/ownership');
@@ -29,7 +30,7 @@ router.post('/:eventId/rename', adminAuth, requirePermission('events.edit'), req
   try {
     const errors = validationResult(req);
     if (!errors.isEmpty()) {
-      return res.status(400).json({ success: false, errors: errors.array() });
+      return res.status(400).json({ success: false, errors: safeValidationErrors(errors) });
     }
 
     const { eventId } = req.params;
@@ -70,7 +71,7 @@ router.post('/:eventId/validate-rename', adminAuth, requirePermission('events.ed
   try {
     const errors = validationResult(req);
     if (!errors.isEmpty()) {
-      return res.status(400).json({ valid: false, errors: errors.array() });
+      return res.status(400).json({ valid: false, errors: safeValidationErrors(errors) });
     }
 
     const { eventId } = req.params;
diff --git a/backend/src/routes/adminEventTypes.js b/backend/src/routes/adminEventTypes.js
index f18f4286..1193476e 100644
--- a/backend/src/routes/adminEventTypes.js
+++ b/backend/src/routes/adminEventTypes.js
@@ -7,6 +7,7 @@
 
 const express = require('express');
 const { body, param, validationResult } = require('express-validator');
+const { safeValidationErrors } = require('../utils/routeHelpers');
 const { logActivity } = require('../database/db');
 const { adminAuth } = require('../middleware/auth');
 const { requirePermission } = require('../middleware/permissions');
@@ -57,7 +58,7 @@ router.get('/:id', adminAuth, requirePermission('settings.view'), [
   try {
     const errors = validationResult(req);
     if (!errors.isEmpty()) {
-      return res.status(400).json({ errors: errors.array() });
+      return res.status(400).json({ errors: safeValidationErrors(errors) });
     }
 
     const { id } = req.params;
@@ -94,7 +95,7 @@ router.post('/', adminAuth, requirePermission('settings.edit'), [
   try {
     const errors = validationResult(req);
     if (!errors.isEmpty()) {
-      return res.status(400).json({ errors: errors.array() });
+      return res.status(400).json({ errors: safeValidationErrors(errors) });
     }
 
     const {
@@ -156,7 +157,7 @@ router.put('/:id', adminAuth, requirePermission('settings.edit'), [
   try {
     const errors = validationResult(req);
     if (!errors.isEmpty()) {
-      return res.status(400).json({ errors: errors.array() });
+      return res.status(400).json({ errors: safeValidationErrors(errors) });
     }
 
     const { id } = req.params;
@@ -196,7 +197,7 @@ router.delete('/:id', adminAuth, requirePermission('settings.edit'), [
   try {
     const errors = validationResult(req);
     if (!errors.isEmpty()) {
-      return res.status(400).json({ errors: errors.array() });
+      return res.status(400).json({ errors: safeValidationErrors(errors) });
     }
 
     const { id } = req.params;
@@ -235,7 +236,7 @@ router.post('/reorder', adminAuth, requirePermission('settings.edit'), [
   try {
     const errors = validationResult(req);
     if (!errors.isEmpty()) {
-      return res.status(400).json({ errors: errors.array() });
+      return res.status(400).json({ errors: safeValidationErrors(errors) });
     }
 
     const { orderedIds } = req.body;
diff --git a/backend/src/routes/adminEvents/archiveBulk.js b/backend/src/routes/adminEvents/archiveBulk.js
index 75533ef4..72c4ecde 100644
--- a/backend/src/routes/adminEvents/archiveBulk.js
+++ b/backend/src/routes/adminEvents/archiveBulk.js
@@ -9,7 +9,7 @@ const { adminAuth } = require('../../middleware/auth');
 const { requirePermission } = require('../../middleware/permissions');
 const { archiveEvent } = require('../../services/archiveService');
 const logger = require('../../utils/logger');
-const { errorResponse } = require('../../utils/routeHelpers');
+const { errorResponse, safeValidationErrors } = require('../../utils/routeHelpers');
 const { requireEventOwnership, filterOwnedEventIds } = require('../../middleware/ownership');
 const { deleteEventCascade } = require('./helpers');
 
@@ -70,7 +70,7 @@ module.exports = (router) => {
     try {
       const errors = validationResult(req);
       if (!errors.isEmpty()) {
-        return res.status(400).json({ errors: errors.array() });
+        return res.status(400).json({ errors: safeValidationErrors(errors) });
       }
 
       const { eventIds } = req.body;
@@ -160,7 +160,7 @@ module.exports = (router) => {
     try {
       const errors = validationResult(req);
       if (!errors.isEmpty()) {
-        return res.status(400).json({ errors: errors.array() });
+        return res.status(400).json({ errors: safeValidationErrors(errors) });
       }
 
       const { eventIds } = req.body;
diff --git a/backend/src/routes/adminEvents/crud.js b/backend/src/routes/adminEvents/crud.js
index 785a909c..85c80da7 100644
--- a/backend/src/routes/adminEvents/crud.js
+++ b/backend/src/routes/adminEvents/crud.js
@@ -17,7 +17,7 @@ const { escapeLikePattern } = require('../../utils/sqlSecurity');
 const { validatePasswordInContext, getBcryptRounds } = require('../../utils/passwordValidation');
 const logger = require('../../utils/logger');
 const { sanitizeForLog, sanitizeValidationErrors } = require('../../utils/sanitizeForLog');
-const { errorResponse } = require('../../utils/routeHelpers');
+const { errorResponse, safeValidationErrors } = require('../../utils/routeHelpers');
 const { buildShareLinkVariants } = require('../../services/shareLinkService');
 const { parseBooleanInput } = require('../../utils/parsers');
 const eventTypeService = require('../../services/eventTypeService');
@@ -157,7 +157,7 @@ module.exports = (router) => {
         // errors.array() embeds the SUBMITTED value per field — including a
         // rejected plaintext password (GHSA-r794).
         logger.error('Validation errors:', sanitizeValidationErrors(errors.array()));
-        return res.status(400).json({ errors: errors.array() });
+        return res.status(400).json({ errors: safeValidationErrors(errors) });
       }
 
       // Get field requirements from settings
@@ -856,7 +856,7 @@ module.exports = (router) => {
     try {
       const errors = validationResult(req);
       if (!errors.isEmpty()) {
-        return res.status(400).json({ errors: errors.array() });
+        return res.status(400).json({ errors: safeValidationErrors(errors) });
       }
 
       const { id } = req.params;
@@ -1017,7 +1017,7 @@ module.exports = (router) => {
     try {
       const errors = validationResult(req);
       if (!errors.isEmpty()) {
-        return res.status(400).json({ errors: errors.array() });
+        return res.status(400).json({ errors: safeValidationErrors(errors) });
       }
 
       const { id } = req.params;
@@ -1295,7 +1295,7 @@ module.exports = (router) => {
       if (!errors.isEmpty()) {
         // Redact credentials — an invalid update still logs the whole body (GHSA-pgmp).
         logger.debug('Update event validation errors', { errors: sanitizeValidationErrors(errors.array()), body: sanitizeForLog(req.body) });
-        return res.status(400).json({ errors: errors.array() });
+        return res.status(400).json({ errors: safeValidationErrors(errors) });
       }
 
       const { id } = req.params;
@@ -1695,7 +1695,7 @@ module.exports = (router) => {
     try {
       const errors = validationResult(req);
       if (!errors.isEmpty()) {
-        return res.status(400).json({ errors: errors.array() });
+        return res.status(400).json({ errors: safeValidationErrors(errors) });
       }
 
       const { id } = req.params;
diff --git a/backend/src/routes/adminEvents/slideshow.js b/backend/src/routes/adminEvents/slideshow.js
index c22ccb57..73bb360d 100644
--- a/backend/src/routes/adminEvents/slideshow.js
+++ b/backend/src/routes/adminEvents/slideshow.js
@@ -8,7 +8,7 @@ const { formatBoolean } = require('../../utils/dbCompat');
 const { adminAuth } = require('../../middleware/auth');
 const { requirePermission } = require('../../middleware/permissions');
 const crypto = require('crypto');
-const { errorResponse } = require('../../utils/routeHelpers');
+const { errorResponse, safeValidationErrors } = require('../../utils/routeHelpers');
 const { parseBooleanInput } = require('../../utils/parsers');
 const { requireEventOwnership } = require('../../middleware/ownership');
 const { requireFeatureFlag } = require('../../middleware/requireFeatureFlag');
@@ -110,7 +110,7 @@ module.exports = (router) => {
     try {
       const errors = validationResult(req);
       if (!errors.isEmpty()) {
-        return res.status(400).json({ error: 'Invalid slideshow settings', details: errors.array() });
+        return res.status(400).json({ error: 'Invalid slideshow settings', details: safeValidationErrors(errors) });
       }
 
       const event = await loadOwnedEvent(req);
diff --git a/backend/src/routes/adminPhotoExport.js b/backend/src/routes/adminPhotoExport.js
index b6e1aa6c..5f65813c 100644
--- a/backend/src/routes/adminPhotoExport.js
+++ b/backend/src/routes/adminPhotoExport.js
@@ -11,7 +11,7 @@ const { adminAuth } = require('../middleware/auth');
 const { requirePermission } = require('../middleware/permissions');
 const { requireEventOwnership } = require('../middleware/ownership');
 const { PhotoFilterBuilder } = require('../utils/photoFilterBuilder');
-const { getPagination } = require('../utils/routeHelpers');
+const { getPagination, safeValidationErrors } = require('../utils/routeHelpers');
 const { PhotoExportService } = require('../services/photoExportService');
 const logger = require('../utils/logger');
 
@@ -39,7 +39,7 @@ router.get('/:eventId/filtered', adminAuth, requirePermission('photos.view'), re
   try {
     const errors = validationResult(req);
     if (!errors.isEmpty()) {
-      return res.status(400).json({ errors: errors.array() });
+      return res.status(400).json({ errors: safeValidationErrors(errors) });
     }
 
     const eventId = parseInt(req.params.eventId);
@@ -166,7 +166,7 @@ router.post('/:eventId/export', adminAuth, requirePermission('photos.download'),
   try {
     const errors = validationResult(req);
     if (!errors.isEmpty()) {
-      return res.status(400).json({ errors: errors.array() });
+      return res.status(400).json({ errors: safeValidationErrors(errors) });
     }
 
     const eventId = parseInt(req.params.eventId);
diff --git a/backend/src/routes/adminRestore.js b/backend/src/routes/adminRestore.js
index 5b69de34..ab2022f3 100644
--- a/backend/src/routes/adminRestore.js
+++ b/backend/src/routes/adminRestore.js
@@ -5,7 +5,7 @@ const { adminAuth } = require('../middleware/auth');
 const { requirePermission } = require('../middleware/permissions');
 const { body, query, validationResult } = require('express-validator');
 const logger = require('../utils/logger');
-const { getPagination } = require('../utils/routeHelpers');
+const { getPagination, safeValidationErrors } = require('../utils/routeHelpers');
 const { db } = require('../database/db');
 const path = require('path');
 const fs = require('fs').promises;
@@ -86,7 +86,7 @@ router.post('/validate', requirePermission('backup.restore'), [
   if (!errors.isEmpty()) {
     return res.status(400).json({
       success: false,
-      errors: errors.array()
+      errors: safeValidationErrors(errors)
     });
   }
 
@@ -158,7 +158,7 @@ router.post('/start', requirePermission('backup.restore'), [
   if (!errors.isEmpty()) {
     return res.status(400).json({
       success: false,
-      errors: errors.array()
+      errors: safeValidationErrors(errors)
     });
   }
 
@@ -690,7 +690,7 @@ router.put('/settings', requirePermission('backup.restore'), [
   if (!errors.isEmpty()) {
     return res.status(400).json({
       success: false,
-      errors: errors.array()
+      errors: safeValidationErrors(errors)
     });
   }
 
diff --git a/backend/src/routes/adminSettings.js b/backend/src/routes/adminSettings.js
index c2e3220f..861ca574 100644
--- a/backend/src/routes/adminSettings.js
+++ b/backend/src/routes/adminSettings.js
@@ -23,7 +23,7 @@ const { sanitizeCss } = require('../utils/cssSanitizer');
 const { upsertAppSetting } = require('../utils/appSettings');
 const { clearShareLinkSettingsCache } = require('../services/shareLinkService');
 const { resetSecurityConfigCache } = require('../utils/authSecurity');
-const { errorResponse } = require('../utils/routeHelpers');
+const { errorResponse, safeValidationErrors } = require('../utils/routeHelpers');
 const logger = require('../utils/logger');
 const { measureLocalStorageUsage } = require('../services/localStorageUsage');
 const router = express.Router();
@@ -1477,7 +1477,7 @@ router.put('/security/rate-limit', adminAuth, requirePermission('settings.edit')
   try {
     const errors = validationResult(req);
     if (!errors.isEmpty()) {
-      return res.status(400).json({ errors: errors.array() });
+      return res.status(400).json({ errors: safeValidationErrors(errors) });
     }
 
     const {
diff --git a/backend/src/routes/adminShortUrls.js b/backend/src/routes/adminShortUrls.js
index 6a3d2759..518d4779 100644
--- a/backend/src/routes/adminShortUrls.js
+++ b/backend/src/routes/adminShortUrls.js
@@ -11,6 +11,7 @@
  */
 const express = require('express');
 const { body, param, validationResult } = require('express-validator');
+const { safeValidationErrors } = require('../utils/routeHelpers');
 const { adminAuth } = require('../middleware/auth');
 const { requirePermission } = require('../middleware/permissions');
 const { requireEventOwnership } = require('../middleware/ownership');
@@ -32,7 +33,7 @@ router.get(
   requireEventOwnership,
   async (req, res) => {
     const errors = validationResult(req);
-    if (!errors.isEmpty()) return res.status(400).json({ errors: errors.array() });
+    if (!errors.isEmpty()) return res.status(400).json({ errors: safeValidationErrors(errors) });
     try {
       const rows = await galleryShortUrlService.listForEvent(parseInt(req.params.eventId, 10));
       res.json({ shortUrls: rows });
@@ -56,7 +57,7 @@ router.post(
   requireEventOwnership,
   async (req, res) => {
     const errors = validationResult(req);
-    if (!errors.isEmpty()) return res.status(400).json({ errors: errors.array() });
+    if (!errors.isEmpty()) return res.status(400).json({ errors: safeValidationErrors(errors) });
     try {
       const row = await galleryShortUrlService.createShortUrl({
         eventId: parseInt(req.params.eventId, 10),
@@ -96,7 +97,7 @@ router.delete(
   param('id').isInt({ min: 1 }),
   async (req, res) => {
     const errors = validationResult(req);
-    if (!errors.isEmpty()) return res.status(400).json({ errors: errors.array() });
+    if (!errors.isEmpty()) return res.status(400).json({ errors: safeValidationErrors(errors) });
     try {
       const ok = await galleryShortUrlService.softDelete(
         parseInt(req.params.id, 10),
diff --git a/backend/src/routes/adminWebhooks.js b/backend/src/routes/adminWebhooks.js
index 2ed920a6..c3217caa 100644
--- a/backend/src/routes/adminWebhooks.js
+++ b/backend/src/routes/adminWebhooks.js
@@ -17,6 +17,7 @@
 
 const express = require('express');
 const { body, query, validationResult } = require('express-validator');
+const { safeValidationErrors } = require('../utils/routeHelpers');
 const { db, logActivity } = require('../database/db');
 const { adminAuth } = require('../middleware/auth');
 const { requirePermission } = require('../middleware/permissions');
@@ -106,7 +107,7 @@ router.post(
   async (req, res) => {
     try {
       const errors = validationResult(req);
-      if (!errors.isEmpty()) return res.status(400).json({ errors: errors.array() });
+      if (!errors.isEmpty()) return res.status(400).json({ errors: safeValidationErrors(errors) });
 
       const { name, url, events, active = true, filter, template } = req.body;
       const { plaintext, preview } = webhookService.generateSecret();
@@ -188,7 +189,7 @@ router.put(
   async (req, res) => {
     try {
       const errors = validationResult(req);
-      if (!errors.isEmpty()) return res.status(400).json({ errors: errors.array() });
+      if (!errors.isEmpty()) return res.status(400).json({ errors: safeValidationErrors(errors) });
 
       const row = await db('webhooks').where({ id: req.params.id }).first();
       if (!row) return res.status(404).json({ error: 'Webhook not found' });
@@ -241,7 +242,7 @@ router.post(
   async (req, res) => {
     try {
       const errors = validationResult(req);
-      if (!errors.isEmpty()) return res.status(400).json({ errors: errors.array() });
+      if (!errors.isEmpty()) return res.status(400).json({ errors: safeValidationErrors(errors) });
 
       const row = await db('webhooks').where({ id: req.params.id }).first();
       if (!row) return res.status(404).json({ error: 'Webhook not found' });
@@ -293,7 +294,7 @@ router.get(
   async (req, res) => {
     try {
       const errors = validationResult(req);
-      if (!errors.isEmpty()) return res.status(400).json({ errors: errors.array() });
+      if (!errors.isEmpty()) return res.status(400).json({ errors: safeValidationErrors(errors) });
 
       const webhookId = req.params.id;
       const exists = await db('webhooks').where({ id: webhookId }).first();
diff --git a/backend/src/routes/auth.js b/backend/src/routes/auth.js
index 8d81451d..69a5371d 100644
--- a/backend/src/routes/auth.js
+++ b/backend/src/routes/auth.js
@@ -26,6 +26,9 @@ const {
 const { endSession } = require('../middleware/sessionTimeout');
 const { revokeToken } = require('../utils/tokenRevocation');
 const { timingSafeEqualStr } = require('../utils/timingSafe');
+// Well-formed bcrypt hash that matches nothing; compared against when there is
+// no account so the unknown-user path costs the same as a wrong password.
+const DUMMY_BCRYPT_HASH = '$2b$10$abcdefghijklmnopqrstuuABCDEFGHIJKLMNOPQRSTUVWXYZ01234';
 const logger = require('../utils/logger');
 const { errorResponse } = require('../utils/routeHelpers');
 const {
@@ -91,8 +94,10 @@ async function completeAdminLogin(req, res, admin, ipAddress, userAgent, lockout
 
 // Admin login with enhanced security
 router.post('/admin/login', [
-  body('username').notEmpty().trim(),
-  body('password').notEmpty()
+  // Length caps: an unbounded username reached the lockout lookup, bcrypt,
+  // the failed-attempt log line and login_attempts.identifier as sent.
+  body('username').isString().trim().notEmpty().isLength({ max: 255 }),
+  body('password').isString().notEmpty().isLength({ max: MAX_PASSWORD_LENGTH })
 ], async (req, res) => {
   try {
     const errors = validationResult(req);
@@ -141,7 +146,13 @@ router.post('/admin/login', [
       .first();
 
     // Use generic error to prevent user enumeration
-    if (!admin || !await bcrypt.compare(password, admin.password_hash)) {
+    // Always run one bcrypt compare so an unknown username costs the same
+    // ~100ms as a wrong password; short-circuiting here was a timing oracle
+    // for username enumeration despite the generic message.
+    const passwordMatches = admin
+      ? await bcrypt.compare(password, admin.password_hash)
+      : await bcrypt.compare(password, DUMMY_BCRYPT_HASH).then(() => false);
+    if (!passwordMatches) {
       await trackFailedAttempt(username, ipAddress, userAgent);
       return res.status(401).json({ error: getGenericAuthError() });
     }
@@ -320,8 +331,8 @@ router.post('/logout', async (req, res) => {
 
 // Gallery password verification with enhanced security
 router.post('/gallery/verify', [
-  body('slug').notEmpty().trim(),
-  body('password').optional().isString()
+  body('slug').isString().trim().notEmpty().isLength({ max: 255 }),
+  body('password').optional().isString().isLength({ max: MAX_PASSWORD_LENGTH })
 ], async (req, res) => {
   try {
     const errors = validationResult(req);
@@ -338,7 +349,7 @@ router.post('/gallery/verify', [
 
     if (!event) {
       // Perform a dummy bcrypt compare to prevent timing-based slug enumeration
-      await bcrypt.compare(password || '', '$2b$10$abcdefghijklmnopqrstuuABCDEFGHIJKLMNOPQRSTUVWXYZ01234');
+      await bcrypt.compare(password || '', DUMMY_BCRYPT_HASH);
       await trackFailedAttempt(`gallery:${slug}`, ipAddress, userAgent);
       return res.status(401).json({ error: 'Invalid gallery or password' });
     }
@@ -432,7 +443,7 @@ router.post('/gallery/verify', [
 
 // Client access login (PIN-based)
 router.post('/gallery/:slug/client-login', [
-  body('password').notEmpty().isString()
+  body('password').notEmpty().isString().isLength({ max: MAX_PASSWORD_LENGTH })
 ], async (req, res) => {
   try {
     const errors = validationResult(req);
diff --git a/backend/src/routes/customer.js b/backend/src/routes/customer.js
index 04ed26df..de48e73e 100644
--- a/backend/src/routes/customer.js
+++ b/backend/src/routes/customer.js
@@ -17,9 +17,9 @@ const jwt = require('jsonwebtoken');
 const { body, param, validationResult } = require('express-validator');
 const { db, logActivity } = require('../database/db');
 const { formatBoolean } = require('../utils/dbCompat');
-const { getBcryptRounds } = require('../utils/passwordValidation');
+const { getBcryptRounds, MAX_PASSWORD_LENGTH } = require('../utils/passwordValidation');
 const logger = require('../utils/logger');
-const { errorResponse } = require('../utils/routeHelpers');
+const { errorResponse, safeValidationErrors } = require('../utils/routeHelpers');
 const { getClientIp } = require('../utils/requestIp');
 const { customerAuth } = require('../middleware/customerAuth');
 const { setGalleryAuthCookies } = require('../utils/tokenUtils');
@@ -147,7 +147,7 @@ router.get('/events/:slug/access-token', [
   try {
     const errors = validationResult(req);
     if (!errors.isEmpty()) {
-      return res.status(400).json({ errors: errors.array() });
+      return res.status(400).json({ errors: safeValidationErrors(errors) });
     }
 
     const { slug } = req.params;
@@ -284,7 +284,7 @@ router.put('/profile', [
   try {
     const errors = validationResult(req);
     if (!errors.isEmpty()) {
-      return res.status(400).json({ errors: errors.array() });
+      return res.status(400).json({ errors: safeValidationErrors(errors) });
     }
 
     // Normalise incoming values: trim strings, drop empty → null so the DB
@@ -329,14 +329,14 @@ router.put('/profile', [
  */
 router.post('/profile/password', [
   customerAuth,
-  body('currentPassword').isString().isLength({ min: 1 }),
-  body('newPassword').isString().isLength({ min: 8 })
+  body('currentPassword').isString().isLength({ min: 1, max: MAX_PASSWORD_LENGTH }),
+  body('newPassword').isString().isLength({ min: 8, max: MAX_PASSWORD_LENGTH })
     .withMessage('Password must be at least 8 characters'),
 ], async (req, res) => {
   try {
     const errors = validationResult(req);
     if (!errors.isEmpty()) {
-      return res.status(400).json({ errors: errors.array() });
+      return res.status(400).json({ errors: safeValidationErrors(errors) });
     }
 
     const { currentPassword, newPassword } = req.body;
diff --git a/backend/src/routes/customerAuth.js b/backend/src/routes/customerAuth.js
index 3abe4642..c9e2169b 100644
--- a/backend/src/routes/customerAuth.js
+++ b/backend/src/routes/customerAuth.js
@@ -16,6 +16,9 @@ const express = require('express');
 const bcrypt = require('bcrypt');
 const jwt = require('jsonwebtoken');
 const { body, param, validationResult } = require('express-validator');
+const { safeValidationErrors } = require('../utils/routeHelpers');
+const { MAX_PASSWORD_LENGTH } = require('../utils/passwordValidation');
+const DUMMY_BCRYPT_HASH = '$2b$10$abcdefghijklmnopqrstuuABCDEFGHIJKLMNOPQRSTUVWXYZ01234';
 const { db, logActivity } = require('../database/db');
 const { formatBoolean } = require('../utils/dbCompat');
 const { verifyRecaptcha } = require('../services/recaptcha');
@@ -65,12 +68,12 @@ const TOKEN_TTL_SECONDS = 24 * 60 * 60; // mirrors admin tokens
 //     gallery JWTs (instant per-gallery revocation).
 router.post('/login', [
   body('email').isEmail().normalizeEmail(IDENTITY_PRESERVING_NORMALIZE_EMAIL).withMessage('Valid email is required'),
-  body('password').isString().notEmpty(),
+  body('password').isString().notEmpty().isLength({ max: MAX_PASSWORD_LENGTH }),
 ], async (req, res) => {
   try {
     const errors = validationResult(req);
     if (!errors.isEmpty()) {
-      return res.status(400).json({ errors: errors.array() });
+      return res.status(400).json({ errors: safeValidationErrors(errors) });
     }
 
     const { email, password, recaptchaToken } = req.body;
@@ -99,7 +102,12 @@ router.post('/login', [
 
     const customer = await db('customer_accounts').where('email', email).first();
     // Generic error to prevent user enumeration — same wording as admin login.
-    if (!customer || !customer.password_hash || !await bcrypt.compare(password, customer.password_hash)) {
+    // One bcrypt compare on every path so an unknown email is not a timing
+    // oracle (the dummy hash matches nothing).
+    const passwordMatches = customer && customer.password_hash
+      ? await bcrypt.compare(password, customer.password_hash)
+      : await bcrypt.compare(password, DUMMY_BCRYPT_HASH).then(() => false);
+    if (!passwordMatches) {
       await trackFailedAttempt(lockoutKey, ipAddress, userAgent);
       return res.status(401).json({ error: getGenericAuthError() });
     }
@@ -273,7 +281,7 @@ router.post('/accept-invite', [
   // Length floor enforced again here for an early reject; the full
   // policy (uppercase + digit) is checked below so we can surface a
   // specific message rather than a generic validator error.
-  body('password').isString().isLength({ min: 8 })
+  body('password').isString().isLength({ min: 8, max: MAX_PASSWORD_LENGTH })
     .withMessage('Password must be at least 8 characters'),
   // Optional structured profile from the accept-invite form. Mirrors
   // the admin prefill shape — anything the customer types here wins
@@ -296,7 +304,7 @@ router.post('/accept-invite', [
   try {
     const errors = validationResult(req);
     if (!errors.isEmpty()) {
-      return res.status(400).json({ errors: errors.array() });
+      return res.status(400).json({ errors: safeValidationErrors(errors) });
     }
     const { token, name, password, profile } = req.body;
 
@@ -355,11 +363,11 @@ router.get('/password-reset/:token', [
  */
 router.post('/password-reset', [
   body('token').isLength({ min: 64, max: 64 }).matches(/^[a-f0-9]+$/i),
-  body('password').isString().isLength({ min: 8 }).withMessage('Password must be at least 8 characters'),
+  body('password').isString().isLength({ min: 8, max: MAX_PASSWORD_LENGTH }).withMessage('Password must be at least 8 characters'),
 ], async (req, res) => {
   try {
     const errors = validationResult(req);
-    if (!errors.isEmpty()) return res.status(400).json({ errors: errors.array() });
+    if (!errors.isEmpty()) return res.status(400).json({ errors: safeValidationErrors(errors) });
     const policyError = validateCustomerPassword(req.body.password);
     if (policyError) {
       return res.status(400).json({
diff --git a/backend/src/routes/setup.js b/backend/src/routes/setup.js
index 1acafbbf..c1916cd1 100644
--- a/backend/src/routes/setup.js
+++ b/backend/src/routes/setup.js
@@ -7,6 +7,8 @@
 // rate-limited at the mount point in server.js (authRateLimiter).
 const express = require('express');
 const { body, validationResult } = require('express-validator');
+const { safeValidationErrors } = require('../utils/routeHelpers');
+const { MAX_PASSWORD_LENGTH } = require('../utils/passwordValidation');
 const setupService = require('../services/setupService');
 const { getClientIp } = require('../utils/requestIp');
 const { setAdminAuthCookie } = require('../utils/tokenUtils');
@@ -31,7 +33,7 @@ router.post('/verify-token', [
 ], async (req, res) => {
   const errors = validationResult(req);
   if (!errors.isEmpty()) {
-    return res.status(400).json({ errors: errors.array() });
+    return res.status(400).json({ errors: safeValidationErrors(errors) });
   }
   try {
     const valid = await setupService.verifySetupToken(req.body.token);
@@ -51,11 +53,11 @@ router.post('/verify-token', [
 router.post('/admin', [
   body('token').notEmpty().withMessage('Setup token is required'),
   body('email').isEmail().withMessage('A valid email is required'),
-  body('password').notEmpty().withMessage('Password is required'),
+  body('password').isString().notEmpty().isLength({ max: MAX_PASSWORD_LENGTH }).withMessage('Password is required'),
 ], async (req, res) => {
   const errors = validationResult(req);
   if (!errors.isEmpty()) {
-    return res.status(400).json({ errors: errors.array() });
+    return res.status(400).json({ errors: safeValidationErrors(errors) });
   }
   try {
     const { token, email, password } = req.body;
diff --git a/backend/src/routes/v1/events.js b/backend/src/routes/v1/events.js
index 6474743e..d562b77a 100644
--- a/backend/src/routes/v1/events.js
+++ b/backend/src/routes/v1/events.js
@@ -18,6 +18,7 @@ const crypto = require('crypto');
 const multer = require('multer');
 const sharp = require('sharp');
 const { body, query, validationResult } = require('express-validator');
+const { safeValidationErrors } = require('../../utils/routeHelpers');
 const { db, logActivity } = require('../../database/db');
 const { apiTokenAuth, requireApiScope } = require('../../middleware/apiTokenAuth');
 const { requireEventOwnership, scopeEventsQuery } = require('../../middleware/ownership');
@@ -146,7 +147,7 @@ router.post(
   async (req, res) => {
     try {
       const errors = validationResult(req);
-      if (!errors.isEmpty()) return res.status(400).json({ errors: errors.array() });
+      if (!errors.isEmpty()) return res.status(400).json({ errors: safeValidationErrors(errors) });
       const {
         event_name, event_type, event_date,
         customer_name = null, customer_email = null, customer_phone = null,
diff --git a/backend/src/utils/feedbackValidation.js b/backend/src/utils/feedbackValidation.js
index eacace87..cc5dd37c 100644
--- a/backend/src/utils/feedbackValidation.js
+++ b/backend/src/utils/feedbackValidation.js
@@ -1,4 +1,5 @@
 const { body, param, validationResult } = require('express-validator');
+const { safeValidationErrors } = require('./routeHelpers');
 const validator = require('validator');
 const { IDENTITY_PRESERVING_NORMALIZE_EMAIL } = require('./emailNormalization');
 
@@ -225,7 +226,7 @@ const checkValidation = (req, res, next) => {
   if (!errors.isEmpty()) {
     return res.status(400).json({
       error: 'Validation failed',
-      errors: errors.array()
+      errors: safeValidationErrors(errors)
     });
   }
   next();
diff --git a/backend/src/utils/routeHelpers.js b/backend/src/utils/routeHelpers.js
index 28d7ce31..43f3b798 100644
--- a/backend/src/utils/routeHelpers.js
+++ b/backend/src/utils/routeHelpers.js
@@ -42,6 +42,15 @@ const handleAsync = (fn) => {
  *   // ... rest of handler
  * }));
  */
+
+/**
+ * express-validator's errors.array() carries `value` -- the submitted input.
+ * Returning it verbatim reflects whatever the caller sent (a rejected
+ * password, a 2mb string) back in the 400 body. Everything except `value` is
+ * kept, so consumers that read `msg` / `path` see no change.
+ */
+const safeValidationErrors = (errors) => errors.array().map(({ value, ...rest }) => rest);
+
 const validateRequest = (req) => {
   const errors = validationResult(req);
   if (!errors.isEmpty()) {
@@ -174,6 +183,7 @@ const paginatedResponse = (data, total, page, limit) => {
 module.exports = {
   handleAsync,
   validateRequest,
+  safeValidationErrors,
   successResponse,
   errorResponse,
   withValidation,