CVE-2025-20051
CRITICALCVE-2025-20051 is a critical-severity (CVSS 9.9) Path Traversal vulnerability in github.com/mattermost/mattermost/server/v8. O3 Security confirms whether CVE-2025-20051 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Arbitrary file read via block duplication in Mattermost Boards
Real-World Exposure
github.com/mattermost/mattermost/server/v8🐹github.com/mattermost/mattermost/server/v8🐹github.com/mattermost/mattermost/server/v8🐹github.com/mattermost/mattermost/server/v8🐹github.com/mattermost/mattermost/server/v8Real-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 10.4.x <= 10.4.1, 9.11.x <= 9.11.7, 10.3.x <= 10.3.2, 10.2.x <= 10.2.2 fail to properly validate input when patching and duplicating a board, which allows a user to read any arbitrary file on the system via duplicating a specially crafted block in Boards.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/mattermost/mattermost/server/v8 | all versions | 8.0.0-20250122165010-4ed702ccff4e |
| 🐹Go | github.com/mattermost/mattermost/server/v8 | ≥ 9.11.0-rc1&&< 9.11.8 | 9.11.8 |
| 🐹Go | github.com/mattermost/mattermost/server/v8 | ≥ 10.2.0-rc1&&< 10.2.3 | 10.2.3 |
| 🐹Go | github.com/mattermost/mattermost/server/v8 | ≥ 10.3.0-rc1&&< 10.3.3 | 10.3.3 |
| 🐹Go | github.com/mattermost/mattermost/server/v8 | ≥ 10.4.0-rc1&&< 10.4.2 | 10.4.2 |
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/v8. 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/v8 to 8.0.0-20250122165010-4ed702ccff4e or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-20051 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-2025-20051 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-2025-20051. 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-2025-20051 in your dependencies?
O3 detects CVE-2025-20051 across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.