diff --git a/packages/auth/server/routes/email-password.ts b/packages/auth/server/routes/email-password.ts
index 1c2bd5d297..ddfceb4961 100644
--- a/packages/auth/server/routes/email-password.ts
+++ b/packages/auth/server/routes/email-password.ts
@@ -4,6 +4,7 @@ import {
   isEmailDomainAllowedForSignup,
   isSigninEnabledForProvider,
   isSignupEnabledForProvider,
+  TIMING_SAFE_DUMMY_PASSWORD_HASH,
 } from '@documenso/lib/constants/auth';
 import { EMAIL_VERIFICATION_STATE } from '@documenso/lib/constants/email';
 import { AppError } from '@documenso/lib/errors/app-error';
@@ -102,6 +103,10 @@ export const emailPasswordRoute = new Hono<HonoAuthContext>()
     // same INVALID_CREDENTIALS error as a wrong password, so probing the
     // endpoint cannot reveal which emails are on the allowlist.
     if (!isSigninEnabledForProvider('email') && !isBreakGlassEmail(email)) {
+      // Equalise timing with the real compare below so measuring response
+      // time cannot reveal allowlist membership either.
+      await compare(password, TIMING_SAFE_DUMMY_PASSWORD_HASH);
+
       throw new AppError(AuthenticationErrorCode.InvalidCredentials, {
         message: 'Invalid email or password',
       });
@@ -118,6 +123,10 @@ export const emailPasswordRoute = new Hono<HonoAuthContext>()
     });
 
     if (!user || !user.password) {
+      // Equalise timing with the real compare below: unknown users and
+      // passwordless accounts must not be distinguishable by response time.
+      await compare(password, TIMING_SAFE_DUMMY_PASSWORD_HASH);
+
       throw new AppError(AuthenticationErrorCode.InvalidCredentials, {
         message: 'Invalid email or password',
       });
diff --git a/packages/lib/constants/auth.test.ts b/packages/lib/constants/auth.test.ts
index 06403ab1e8..5dffb9d47e 100644
--- a/packages/lib/constants/auth.test.ts
+++ b/packages/lib/constants/auth.test.ts
@@ -1,6 +1,12 @@
 import { afterEach, describe, expect, it, vi } from 'vitest';
 
-import { getBreakGlassEmails, isBreakGlassEmail, isBreakGlassSigninEnabled } from './auth';
+import {
+  getBreakGlassEmails,
+  isBreakGlassEmail,
+  isBreakGlassSigninEnabled,
+  SALT_ROUNDS,
+  TIMING_SAFE_DUMMY_PASSWORD_HASH,
+} from './auth';
 
 describe('break-glass password signin allowlist', () => {
   afterEach(() => {
@@ -33,3 +39,14 @@ describe('break-glass password signin allowlist', () => {
     expect(isBreakGlassEmail('')).toBe(false);
   });
 });
+
+describe('timing-safe dummy password hash', () => {
+  it('is a bcrypt hash at the same cost factor as real password hashing', () => {
+    // bcrypt format: $<variant>$<cost>$<22-char salt><31-char hash>
+    const parts = TIMING_SAFE_DUMMY_PASSWORD_HASH.split('$');
+
+    expect(parts[1]).toMatch(/^2[aby]$/);
+    expect(Number(parts[2])).toBe(SALT_ROUNDS);
+    expect(TIMING_SAFE_DUMMY_PASSWORD_HASH).toHaveLength(60);
+  });
+});
diff --git a/packages/lib/constants/auth.ts b/packages/lib/constants/auth.ts
index 20230a0e5f..f995c339fe 100644
--- a/packages/lib/constants/auth.ts
+++ b/packages/lib/constants/auth.ts
@@ -5,6 +5,16 @@ import { NEXT_PUBLIC_WEBAPP_URL } from './app';
 
 export const SALT_ROUNDS = 12;
 
+/**
+ * Precomputed bcrypt hash (cost = SALT_ROUNDS) of an unguessable string.
+ * Compared against the submitted password on early-rejected signin attempts
+ * (signin disabled suite-wide, unknown user, user without a password) so
+ * every failing path pays the same bcrypt cost and the endpoint cannot be
+ * probed by measuring verification time. Never validates anything: any
+ * compare against it returns false.
+ */
+export const TIMING_SAFE_DUMMY_PASSWORD_HASH = '$2y$12$eAJ6CR54acEljh1J/AN.peIPUd19yidDQRKhynGQriewBgzF1bQdm';
+
 export const IDENTITY_PROVIDER_NAME: Record<string, string> = {
   DOCUMENSO: 'Documenso',
   GOOGLE: 'Google',