Vulnerability · Published Oct 16, 2026 · Assigned by Mattermost
CVE-2026-18795Missing server side validation allowed user to quarantine a DM and GM post
Medium 6.4
In plain English
A medium-severity missing authorization in Mattermost from Mattermost. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.1% (higher than 4% of all known vulnerabilities).
Severity (CVSS 3.1)6.4Medium
Exploit odds (30 days)0.1%top 95.8% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
Official description
Mattermost versions 11.10.x <= 11.10.0, 11.7.x <= 11.7.9, 11.9.x <= 11.9.1, 11.8.x <= 11.8.5 fail to enforce DM/GM check on server side which allows an authenticated user to quarantine a post belonging to DM or GM via direct API call.. Mattermost Advisory ID: MMSA-2026-00756
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Mattermost | Mattermost | 11.10.0 – through 11.10.011.7.0 – through 11.7.911.9.0 – through 11.9.111.8.0 – through 11.8.5 |
Weakness: CWE-862 · Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:L
References
- MMSA-2026-00756 vendor-advisory