GHSA-mxxh-fmjq-j6x4
LOWGHSA-mxxh-fmjq-j6x4 is a low-severity (CVSS 2.7) CWE-862 vulnerability in github.com/mattermost/mattermost-server. O3 Security confirms whether GHSA-mxxh-fmjq-j6x4 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Mattermost doesn't validate whether users were correctly owned by the correct Connected Workspace
Blast Radius
github.com/mattermost/mattermost-serverReal-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 <= 10.11.12 fail to validate whether users were correctly owned by the correct Connected Workspace which allows a malicious remote server connected using the Conntexted Workspaces feature to change the displayed status of local users via the Connected Workspaces API. Mattermost Advisory ID: MMSA-2026-00603.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/mattermost/mattermost-server | ≥ 8.0.0-20250721062209-4952acea88ce&&< 8.0.0-20260316060126-bc1a2b34b1f9 | 8.0.0-20260316060126-bc1a2b34b1f9 |
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 8.0.0-20260316060126-bc1a2b34b1f9 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-mxxh-fmjq-j6x4 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 GHSA-mxxh-fmjq-j6x4 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 GHSA-mxxh-fmjq-j6x4. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-mxxh-fmjq-j6x4 in your dependencies?
O3 detects GHSA-mxxh-fmjq-j6x4 across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.