Vulnerability · Published Sep 14, 2026 · Assigned by Mattermost

CVE-2026-10542Playbooks channel action update validation issue

Medium 5.0

In plain English

A medium-severity authorization bypass via user-controlled key 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 2% of all known vulnerabilities).

Severity (CVSS 3.1)5.0Medium

Exploit odds (30 days)0.1%top 98.2% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

Mattermost versions 11.9.x <= 11.9.0, 11.8.x <= 11.8.4, 11.7.x <= 11.7.7, 10.11.x <= 10.11.22 fail to validate channel action ownership which allows channel managers to update actions in other channels via the channel action update endpoint.. Mattermost Advisory ID: MMSA-2026-00692

Affected products (as reported)

Vendor	Product	Versions
Mattermost	Mattermost	11.9.0 – through 11.9.011.8.0 – through 11.8.411.7.0 – through 11.7.710.11.0 – through 10.11.22

Weakness: CWE-639 · Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:L

References

MMSA-2026-00692 vendor-advisory