CVE-2025-11777
MEDIUMMattermost Incorrect Authorization vulnerability
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
github.com/mattermost/mattermost-server🐹github.com/mattermost/mattermost-server🐹github.com/mattermost/mattermost/server/v8🐹github.com/mattermost/mattermost🐹github.com/mattermost/mattermost-server🐹github.com/mattermost/mattermost-server/v5🐹github.com/mattermost/mattermost-server/v6Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
Mattermost versions 10.11.x <= 10.11.3, 10.5.x <= 10.5.11 fail to properly validate team membership permissions in the Add Channel Member API which allows users from one team to access user metadata and channel membership information from other teams via the API endpoint
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/mattermost/mattermost-server | ≥ 10.11.0&&< 10.11.4 | 10.11.4 |
| 🐹Go | github.com/mattermost/mattermost-server | ≥ 10.5.0&&< 10.5.12 | 10.5.12 |
| 🐹Go | github.com/mattermost/mattermost/server/v8 | all versions | 8.0.0-20250905150616-ba86dfc5876b |
| 🐹Go | github.com/mattermost/mattermost | all versions | 5.3.2-0.20250905150616-ba86dfc5876b |
| 🐹Go | github.com/mattermost/mattermost-server | all versions | 5.3.2-0.20250905150616-ba86dfc5876b |
| 🐹Go | github.com/mattermost/mattermost-server/v5 | all versions | 5.3.2-0.20250905150616-ba86dfc5876b |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/mattermost/mattermost-server. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update github.com/mattermost/mattermost-server to 10.11.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-11777 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2025-11777 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2025-11777. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2025-11777 in your dependencies?
O3 detects CVE-2025-11777 across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.