CVE-2025-53971: Mattermost Fails to Properly Validate Team Role Modification

August 21, 2025 (updated August 29, 2025)

Mattermost versions 10.5.x <= 10.5.8, 9.11.x <= 9.11.17 fail to properly validate authorization for team scheme role modifications which allows Team Admins to demote Team Members to Guests via the PUT /api/v4/teams/team-id/members/user-id/schemeRoles API endpoint.

References

github.com/advisories/GHSA-4276-cm8c-788h
github.com/mattermost/mattermost
mattermost.com/security-updates
nvd.nist.gov/vuln/detail/CVE-2025-53971
pkg.go.dev/vuln/GO-2025-3902

Code Behaviors & Features

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