CVE-2026-3108
HIGHCVE-2026-3108 is a high-severity (CVSS 8) CWE-150 vulnerability in github.com/mattermost/mattermost/server/v8. O3 Security confirms whether CVE-2026-3108 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Terminal Escape Injection in mmctl Report Posts Command
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 11.2.x <= 11.2.2, 10.11.x <= 10.11.10, 11.4.x <= 11.4.0, 11.3.x <= 11.3.1 fail to sanitize user-controlled post content in the mmctl commands terminal output which allows attackers to manipulate administrator terminals via crafted messages containing ANSI and OSC escape sequences that enable screen manipulation, fake prompts, and clipboard hijacking.. Mattermost Advisory ID: MMSA-2026-00599
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/mattermost/mattermost/server/v8 | ≥ 11.4.0-rc1&&< 11.4.1 | 11.4.1 |
| 🐹Go | github.com/mattermost/mattermost/server/v8 | ≥ 11.3.0-rc1&&< 11.3.2 | 11.3.2 |
| 🐹Go | github.com/mattermost/mattermost/server/v8 | ≥ 11.2.0-rc1&&< 11.2.3 | 11.2.3 |
| 🐹Go | github.com/mattermost/mattermost/server/v8 | ≥ 10.11.0-rc1&&< 10.11.11 | 10.11.11 |
| 🐹Go | github.com/mattermost/mattermost/server/v8 | ≥ 8.0.0-20260105080200-d27a2195068d&&< 8.0.0-20260217110922-b7d4a1f1f59b | 8.0.0-20260217110922-b7d4a1f1f59b |
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 11.4.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-3108 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-2026-3108 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-2026-3108. 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-2026-3108 in your dependencies?
O3 detects CVE-2026-3108 across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.