CVE-2026-0999: Mattermost fails to properly validate login method restrictions

February 16, 2026 (updated February 19, 2026)

Mattermost versions 11.1.x <= 11.1.2, 10.11.x <= 10.11.9, 11.2.x <= 11.2.1 fail to properly validate login method restrictions which allows an authenticated user to bypass SSO-only login requirements via userID-based authentication. Mattermost Advisory ID: MMSA-2025-00548

References

github.com/advisories/GHSA-3c9r-7f29-qp32
github.com/mattermost/mattermost
github.com/mattermost/mattermost/commit/61651b0df7ea5db55d1e54f8d6fb5fce4149309c
mattermost.com/security-updates
nvd.nist.gov/vuln/detail/CVE-2026-0999

Code Behaviors & Features

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