Mattermost is vulnerable to CPU exhaustion via crafted HTTP requestGHSA-9r42-rhw3-2222
LOWFix: mattermost/mattermost@4d86263GHSA-9r42-rhw3-2222 is a low-severity (CVSS 3.1) CWE-407 vulnerability in github.com/mattermost/mattermost-server. A fix is available for github.com/mattermost/mattermost-server — 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-9r42-rhw3-2222.
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🐹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 <= 10.11.8 fail to validate input size before processing hashtags which allows an authenticated attacker to exhaust CPU resources via a single HTTP request containing a post with thousands space-separated tokens.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/mattermost/mattermost-server | ≥ 10.11.0&&< 10.11.9 | 10.11.9go get github.com/mattermost/mattermost-server@v10.11.9 |
| 🐹Go | github.com/mattermost/mattermost-server | ≥ 11.0.0&&< 11.2.0 | 11.2.0go get github.com/mattermost/mattermost-server@v11.2.0 |
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, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/mattermost/mattermost-server to 10.11.9 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-9r42-rhw3-2222 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.
Frequently Asked Questions
Is GHSA-9r42-rhw3-2222 in your dependencies?
Find it across Go, including transitive dependencies.