Mattermost GitHub Plugin Bot Identity Validation Bypass Allows Arbitrary GitHub Reaction InjectionGHSA-jf5h-xfw4-p8gp
LOWFix: mattermost/mattermost-plugin-github@0deffcfGHSA-jf5h-xfw4-p8gp is a low-severity (CVSS 3) CWE-1287 vulnerability in github.com/mattermost/mattermost/server/v8. A fix is available for github.com/mattermost/mattermost/server/v8 — see the affected versions and patch details below.
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-jf5h-xfw4-p8gp.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
github.com/mattermost/mattermost/server/v8🐹github.com/mattermost/mattermost🐹github.com/mattermost/mattermost🐹github.com/mattermost/mattermost-plugin-githubReal-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 <= 10.11.6 and Mattermost GitHub plugin versions <=2.4.0 fail to validate plugin bot identity in reaction forwarding which allows attackers to hijack the GitHub reaction feature to make users add reactions to arbitrary GitHub objects via crafted notification posts.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/mattermost/mattermost/server/v8 | ≥ 10.11.0-rc1&&< 10.11.7-0.20251106103514-3b05384dd014 | 10.11.7-0.20251106103514-3b05384dd014go get github.com/mattermost/mattermost/server/v8@v10.11.7-0.20251106103514-3b05384dd014 |
| 🐹Go | github.com/mattermost/mattermost | all versions | 10.11.7-0.20251106103514-3b05384dd014go get github.com/mattermost/mattermost@v10.11.7-0.20251106103514-3b05384dd014 |
| 🐹Go | github.com/mattermost/mattermost | ≥ 11.0.0-alpha.1&&< 11.1.0 | 11.1.0go get github.com/mattermost/mattermost@v11.1.0 |
| 🐹Go | github.com/mattermost/mattermost-plugin-github | all versions | 1.0.1-0.20250829075715-0deffcfc6beego get github.com/mattermost/mattermost-plugin-github@v1.0.1-0.20250829075715-0deffcfc6bee |
Affected Products
mattermost servermattermostDetection & 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, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/mattermost/mattermost/server/v8 to 10.11.7-0.20251106103514-3b05384dd014 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-jf5h-xfw4-p8gp 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.
Frequently Asked Questions
Is GHSA-jf5h-xfw4-p8gp in your dependencies?
Find it across Go, including transitive dependencies.