Quick answers
- Is CVE-2026-18795 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-18795 being exploited in the wild.
- How severe is CVE-2026-18795?
- Medium severity, with a CVSS score of 6.4, published 16 October 2026.
- Which products and versions are affected?
- Mattermost Server 11.10.0, 11.9.0–11.9.1, 11.8.0–11.8.5, 11.7.0–11.7.9.
- Is there a fix for CVE-2026-18795?
- No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
- How is CVE-2026-18795 attacked?
- It is attacked over the network, in a web application.
- Am I affected by CVE-2026-18795?
- Check whether you run Mattermost Server at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
The vulnerability is an authorization bypass in Mattermost's API where the server fails to enforce DM/GM (direct message/group message) access controls. An authenticated user can call the API directly to quarantine posts in private conversations without proper permission validation. The flaw requires valid authentication but allows lateral privilege escalation within the messaging system.
Affected products
- Mattermost Mattermost Server 11.10.0, 11.9.0–11.9.1, 11.8.0–11.8.5, 11.7.0–11.7.9
Timeline
- 2026-10-16: disclosed