Craft CMS Time-of-check Time-of-use (TOCTOU) Race Condition Vulnerability - CVE-2026-27128

Craft is a content management system (CMS). In versions 4.5.0-RC1 through 4.16.18 and 5.0.0-RC1 through 5.8.22 a Time-of-Check-Time-of-Use (TOCTOU) race condition exists in Craft CMSs token validation service for tokens that explicitly set a limited usage. The getTokenRoute() method reads a tokens usage count checks if its within limits then updates the database in separate non-atomic operations. By sending concurrent requests an attacker can use a single-use impersonation token multiple times before the database update completes. To make this work an attacker needs to obtain a valid user account impersonation URL with a non-expired token via some other means and exploit a race condition while bypassing any rate-limiting rules in place. For this to be a privilege escalation the impersonation URL must include a token for a user account with more permissions than the current user. Versions 4.16.19 and 5.8.23 patch the issue.