Time-of-check Time-of-use (TOCTOU) Race Condition Affecting github.com/mattermost/mattermost/server/channels/app package, versions <10.11.13>=11.3.0-rc1 <11.3.3>=11.4.0-rc1 <11.4.3>=11.5.0-rc1 <11.5.1
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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Test your applications- Snyk IDSNYK-GOLANG-GITHUBCOMMATTERMOSTMATTERMOSTSERVERCHANNELSAPP-16322707
- published30 Apr 2026
- disclosed17 Apr 2026
- creditUnknown
Introduced: 17 Apr 2026
CVE-2026-3590 Â (opens in a new tab)How to fix?
Upgrade github.com/mattermost/mattermost/server/channels/app to version 10.11.13, 11.3.3, 11.4.3, 11.5.1 or higher.
Overview
github.com/mattermost/mattermost/server/channels/app is a private-cloud Slack alternative
Affected versions of this package are vulnerable to Time-of-check Time-of-use (TOCTOU) Race Condition in the authentication process. An attacker can gain unauthorized access to multiple authenticated sessions by reusing a valid guest magic link token through concurrent requests.