Moderate severityNVD Advisory· Published Feb 16, 2026· Updated Feb 17, 2026
Authentication bypass via userID login when email and username login are disabled
CVE-2026-0999
Description
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
AI Insight
LLM-synthesized narrative grounded in this CVE's description and references.
Affected packages
Versions sourced from the GitHub Security Advisory.
| Package | Affected versions | Patched versions |
|---|---|---|
github.com/mattermost/mattermost/server/v8Go | < 8.0.0-20251212052346-61651b0df7ea | 8.0.0-20251212052346-61651b0df7ea |
github.com/mattermost/mattermost-serverGo | >= 11.1.0 | — |
github.com/mattermost/mattermost-serverGo | >= 10.11.0 | — |
github.com/mattermost/mattermost-serverGo | >= 11.2.0 | — |
github.com/mattermost/mattermost-serverGo | < 5.3.2-0.20251212052346-61651b0df7ea | 5.3.2-0.20251212052346-61651b0df7ea |
Affected products
4- ghsa-coords3 versionspkg:golang/github.com/mattermost/mattermost-serverpkg:golang/github.com/mattermost/mattermost/server/v8pkg:rpm/opensuse/govulncheck-vulndb&distro=openSUSE%20Leap%2015.6
>= 11.1.0+ 2 more
- (no CPE)range: >= 11.1.0
- (no CPE)range: < 8.0.0-20251212052346-61651b0df7ea
- (no CPE)range: < 0.0.20260226T182644-150000.1.149.1
- Range: 11.1.0
Patches
Vulnerability mechanics
References
4- github.com/advisories/GHSA-3c9r-7f29-qp32ghsaADVISORY
- mattermost.com/security-updatesghsavendor-advisoryWEB
- nvd.nist.gov/vuln/detail/CVE-2026-0999ghsaADVISORY
- github.com/mattermost/mattermost/commit/61651b0df7ea5db55d1e54f8d6fb5fce4149309cghsaWEB
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