What is CVE-2026-10527?

CVE-2026-10527 is a medium-severity vulnerability in Mattermost, classified under Incorrect Authorization. CVSS score: 6.3/10. Published 2026-08-17.

How severe is CVE-2026-10527?

Medium severity. CVSS v3 base score is 6.3 out of 10.

Auth bypass in Mattermost

CVE-2026-10527

Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21, 11.8.x <= 11.8.3 fails to reconcile SchemeAdmin flags with a user's current role which allows a user demoted to System Guest to retain Board Admin privileges and perform admin-only operations via the Boards REST API or UI.. Mattermost Advisory ID: MMSA-2026-00691

Vulnerability class: Broken Access Control

CVSS v3 metric

CVSS v3 base score 6.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L.

Affected products

Mattermost — versions 11.7.0, 10.11.0, 11.8.0

Weakness classification (CWE)

CWE-863 — Incorrect Authorization

References

responsibledisclosure@mattermost.com (vendor-advisory)

Frequently asked questions

What is CVE-2026-10527?: CVE-2026-10527 is a medium-severity vulnerability in Mattermost, classified under Incorrect Authorization. CVSS score: 6.3/10. Published 2026-08-17.
How severe is CVE-2026-10527?: Medium severity. CVSS v3 base score is 6.3 out of 10.