CVE-2026-82920 PUBLISHED

Mattermost ABAC parent policy bypass via policy update endpoint

Assigner: Mattermost
Reserved: 31.08.2026 Published: 14.09.2026 Updated: 14.09.2026

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

Metrics

CVSS 3.1

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:L/I:L/A:N
CVSS Score: 5.5

Attack Vector	Network	Scope	Changed
Attack Complexity	Low	Confidentiality Impact	Low
Privileges Required	High	Integrity Impact	Low
User Interaction	None	Availability Impact	None

CVSS 3.1

Product Status

Vendor	Mattermost
Product	Mattermost
Versions	Default: unaffected affected from 11.9.0 to 11.9.0 (incl.) affected from 11.8.0 to 11.8.4 (incl.) affected from 11.7.0 to 11.7.7 (incl.) Version 11.10.0 is unaffected Version 11.9.1 is unaffected Version 11.8.5 is unaffected Version 11.7.8 is unaffected

Solutions

Update Mattermost to versions 11.10.0, 11.9.1, 11.8.5, 11.7.8 or higher.

Credits

kiwi_71 finder

References

MMSA-2026-00724

Problem Types

CWE-863: Incorrect Authorization CWE