CVE-2026-9859 Affecting mattermost-10.11-compat package, versions <10.11.22-r0
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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- published22 Aug 2026
- disclosed17 Aug 2026
Introduced: 17 Aug 2026
CVE-2026-9859 (opens in a new tab)How to fix?
Upgrade Minimos:latest mattermost-10.11-compat to version 10.11.22-r0 or higher.
NVD Description
Note: Versions mentioned in the description apply only to the upstream mattermost-10.11-compat package and not the mattermost-10.11-compat package as distributed by Minimos.
See How to fix? for Minimos:latest relevant fixed versions and status.
Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21, 11.8.x <= 11.8.3 fail to enforce PermissionManageBoardRoles on the channelId field of the batch endpoint, which allows an authenticated board editor to relink any board they can edit to an arbitrary channel via a crafted PATCH request. Mattermost Advisory ID: MMSA-2026-00686