Time-of-check Time-of-use (TOCTOU) Race Condition Affecting github.com/mattermost/mattermost/server/channels/api4 package, versions >=10.11.0 <10.11.10>=11.0.0-alpha.1 <11.3.0-rc2
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Start learning- Snyk IDSNYK-GOLANG-GITHUBCOMMATTERMOSTMATTERMOSTSERVERCHANNELSAPI4-15282851
- published15 Feb 2026
- disclosed13 Feb 2026
- creditJuho Forsén
Introduced: 13 Feb 2026
CVE-2026-20796 (opens in a new tab)How to fix?
Upgrade github.com/mattermost/mattermost/server/channels/api4 to version 10.11.10, 11.3.0-rc2 or higher.
Overview
Affected versions of this package are vulnerable to Time-of-check Time-of-use (TOCTOU) Race Condition via a race condition in the /common_teams API endpoint. An attacker can gain unauthorized access to team names by exploiting the timing of channel membership validation during data retrieval. This is only exploitable if a user is deactivated while a request is being processed.