What is CVE-2026-10542?

CVE-2026-10542 is a medium-severity vulnerability in Mattermost, classified under Authorization Bypass Through User-Controlled Key. CVSS score: 5.0/10. Published 2026-09-14.

How severe is CVE-2026-10542?

Medium severity. CVSS v3 base score is 5.0 out of 10.

Auth bypass in Mattermost

CVE-2026-10542

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

Vulnerability class: IDOR (Insecure Direct Object Reference)

CVSS v3 metric

CVSS v3 base score 5.0 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:L.

Affected products

Mattermost

Weakness classification (CWE)

CWE-639 — Authorization Bypass Through User-Controlled Key

References

responsibledisclosure@mattermost.com (vendor-advisory)

Frequently asked questions

What is CVE-2026-10542?: CVE-2026-10542 is a medium-severity vulnerability in Mattermost, classified under Authorization Bypass Through User-Controlled Key. CVSS score: 5.0/10. Published 2026-09-14.
How severe is CVE-2026-10542?: Medium severity. CVSS v3 base score is 5.0 out of 10.