CVE-2024-39274 — server
HIGHCVE-2024-39274 is a high-severity (CVSS 8.7) CWE-284 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.
Malicious remote can add users to arbitrary teams and channels
Exploitation Status
No confirmed exploitation observed yet
- A successful exploit gives an attacker total control of the affected component, not partial access.
- 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 CVE-2024-39274.
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/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 9.9.x <= 9.9.0, 9.5.x <= 9.5.6, 9.7.x <= 9.7.5 and 9.8.x <= 9.8.1 fail to properly validate that the channel that comes from the sync message is a shared channel, when shared channels are enabled, which allows a malicious remote to add users to arbitrary teams and channels
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/mattermost/mattermost/server/v8 | ≥ 9.5.0&&< 9.5.7 | 9.5.7go get github.com/mattermost/mattermost/server/v8@v9.5.7 |
| 🐹Go | github.com/mattermost/mattermost/server/v8 | ≥ 9.7.0&&< 9.7.6 | 9.7.6go get github.com/mattermost/mattermost/server/v8@v9.7.6 |
| 🐹Go | github.com/mattermost/mattermost/server/v8 | ≥ 9.8.0&&< 9.8.2 | 9.8.2go get github.com/mattermost/mattermost/server/v8@v9.8.2 |
| 🐹Go | github.com/mattermost/mattermost/server/v8 | ≥ 9.9.0&&< 9.9.1 | 9.9.1go get github.com/mattermost/mattermost/server/v8@v9.9.1 |
Affected Products
mattermostmattermostDetection & 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 9.5.7 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2024-39274 is resolved across your whole dependency graph.
Workarounds
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.
Frequently Asked Questions
Is CVE-2024-39274 in your dependencies?
Find it across Go, including transitive dependencies.