CVE-2026-3637: Mattermost doesn't check the create_post channel permission during post edit operations

May 18, 2026 (updated June 1, 2026)

Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 fail to check the create_post channel permission during post edit operations which allows an authenticated attacker with revoked posting privileges to modify their existing posts via direct API requests to the post update and patch endpoints.. Mattermost Advisory ID: MMSA-2026-00627

References

github.com/advisories/GHSA-v549-xx3c-6pc8
github.com/mattermost/mattermost/commit/090408f09f53ffc9afc6c65c7c7c1fd3a8cd22f3
mattermost.com/security-updates
nvd.nist.gov/vuln/detail/CVE-2026-3637

Code Behaviors & Features

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