CVE-2026-33877 ApostropheCMS: User Enumeration via Timing Side Channel in Password Reset Endpoint
Unauthenticated attackers can enumerate valid usernames and emails via timing differences in the password reset endpoint, facilitating credential stuffing and phishing.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-33877?
CVE-2026-33877 is a low-severity vulnerability in apostrophecms apostrophe, published on 15 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
ApostropheCMS is an open-source Node.js content management system. Versions 4.28.0 and prior contain a timing side-channel vulnerability in the password reset endpoint (/api/v1/@apostrophecms/login/reset-request) that allows unauthenticated username and email enumeration. When a user is not found, the handler returns after a fixed 2-second artificial delay, but when a valid user is found, it performs a MongoDB update and SMTP email send with no equivalent delay normalization, producing measurably different response times. The endpoint also accepts both username and email via an $or query, and has no rate limiting as the existing checkLoginAttempts throttle only applies to the login flow. This enables automated enumeration of valid accounts for use in credential stuffing or targeted phishing. Only instances that have explicitly enabled the passwordReset option are affected, as it defaults to false. This issue has been fixed in version 4.29.0.
Weakness: CWE-208
Which versions are affected by CVE-2026-33877?
2 open source packages ship an affected version, including apostrophe. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
apostrophe npm | All versions | 4.29.0 |
apostrophe npm | All versions | 4.29.0 |
Products include Apostrophecms Apostrophecms.
How do I fix CVE-2026-33877?
Upgrade apostrophe to 4.29.0 or later.
Is CVE-2026-33877 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-33877 exists.
Other vulnerabilities in apostrophecms apostrophe
- CVE-2021-25979 Apostrophe - Insufficient Session Expiration
- CVE-2026-35569 ApostropheCMS: Stored XSS in SEO Fields Leads to Authenticated API Data Exposure in ApostropheCMS
- CVE-2026-32730 ApostropheCMS MFA/TOTP Bypass via Incorrect MongoDB Query in Bearer Token Middleware
- CVE-2026-40186 ApostropheCMS: sanitize-html allowedTags Bypass via Entity-Decoded Text in nonTextTags Elements
- CVE-2026-33889 ApostropheCMS: Stored XSS via CSS Custom Property Injection in `@apostrophecms/color-field` Escaping Style Tag Context
Sources
Also known as GHSA-mj7r-x3h3-7rmr.