A Time-of-Check-Time-of-Use (TOCTOU) race condition exists in Craft CMS’s token validation service for tokens that explicitly set a limited usage. The getTokenRoute() method reads a token’s usage count, checks if it’s 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.
https://github.com/craftcms/cms/commit/3e4afe18279951c024c64896aa2b93cda6d95fdf
| Score | Percentile |
|---|---|
| 0.01% | 0.61% |
| Base score | Version | Severity | Vector |
|---|---|---|---|
| 6.9 | 4.0 | — |
|
| Type | Value |
|---|---|
| GHSA | GHSA-6fx5-5cw5-4897 ↗ |
| CVE | CVE-2026-27128 ↗ |
| CWE id | Name |
|---|---|
| CWE-367 | Time-of-check Time-of-use (TOCTOU) Race Condition |
Vulnerable version ranges and first patched releases as published by GitHub.
| Ecosystem | Package | Vulnerable range | First patched | Vulnerable functions |
|---|---|---|---|---|
| composer | craftcms/cms | >= 4.5.0-RC1, <= 4.16.18 | 4.16.19 | — |
| composer | craftcms/cms | >= 5.0.0-RC1, <= 5.8.22 | 5.8.23 | — |