CVE-2026-33877: ApostropheCMS: User Enumeration via Timing Side Channel in Password Reset Endpoint

Vulnerability summary

CVE-2026-33877 is a low (CVSS 3.7) Observable Timing Discrepancy vulnerability in apostrophecms apostrophe. EPSS estimates a 0.32% chance of exploitation in the next 30 days, higher than 23.5% of scored vulnerabilities. 1 public exploit is recorded.

Timeline

1. 15-04-2026
   PublishedVulnerability first disclosed.
2. 15-04-2026
   Last modifiedVulnerability information updated.

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.

• CWE-208Observable Timing DiscrepancyTwo separate operations in a product require different amounts of time to complete, in a way that is observable to an actor and reveals security-relevant information about the state of the product, such as whether a particular operation was successful or not.