Vulnerability · Published Sep 14, 2026 · Assigned by Mattermost

CVE-2026-82920Mattermost ABAC parent policy bypass via policy update endpoint

Medium 5.5

In plain English

A medium-severity incorrect authorization 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 0.3% (higher than 17% of all known vulnerabilities).

Severity (CVSS 3.1)5.5Medium

Exploit odds (30 days)0.3%top 82.8% 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 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 (as reported)

Vendor	Product	Versions
Mattermost	Mattermost	11.9.0 – through 11.9.011.8.0 – through 11.8.411.7.0 – through 11.7.7

Weakness: CWE-863 · Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:L/I:L/A:N

References

MMSA-2026-00724 vendor-advisory