Skip to content
OpenAdvisories
Medium · 5.5 CVE-2026-82920 EUVD-2026-77487GHSA-v87m-p66q-xcjg

Mattermost ABAC parent policy bypass via policy update endpoint

Published Sep 14, 2026 · Updated Sep 14, 2026 · Assigned by Mattermost

Description

Mattermost versions 11.9.x <= 11.9.0, 11.8.x <= 11.8.4, 11.7.x <= 11.7.7 fail to enforce authorization boundaries on the access control policy update endpoint which allows a channel or team administrator to detach a system-assigned ABAC parent policy via a crafted PUT /api/v4/access_control_policies request with an empty imports list.. Mattermost Advisory ID: MMSA-2026-00724

Affected products

VendorProductAffectedFixed
Mattermost Mattermost 11.9.0 – ≤ 11.9.0, 11.8.0 – ≤ 11.8.4, 11.7.0 – ≤ 11.7.7 11.10.0

References