CVE-2026-9571

Deactivated user accounts can continue to obtain valid OAuth access tokens via refresh token grant in Mattermost

Published Jul 13, 2026 CVSS 3.1 · 5.9 Medium EPSS < 1% KEV · Not listed
Description
Mattermost versions 11.7.x <= 11.7.2, 11.6.x <= 11.6.4, 10.11.x <= 10.11.19 fail to invalidate OAuth refresh tokens upon user account deactivation, which allows a deactivated user or an attacker in possession of a valid refresh token to obtain new functional access tokens via the OAuth refresh token grant endpoint.. Mattermost Advisory ID: MMSA-2026-00680

Remediation

Vendor Solution

Update Mattermost to versions 11.8.0, 11.7.3, 11.6.5, 10.11.20 or higher.

Tracking

Sign in to view the affected projects.

Advisories

No advisories available
References
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Mattermost
Mattermost mattermost
Vendors & Products Mattermost
Mattermost mattermost
Type Values Removed Values Added
Description Mattermost versions 11.7.x <= 11.7.2, 11.6.x <= 11.6.4, 10.11.x <= 10.11.19 fail to invalidate OAuth refresh tokens upon user account deactivation, which allows a deactivated user or an attacker in possession of a valid refresh token to obtain new functional access tokens via the OAuth refresh token grant endpoint.. Mattermost Advisory ID: MMSA-2026-00680
Title Deactivated user accounts can continue to obtain valid OAuth access tokens via refresh token grant in Mattermost
Weaknesses CWE-305
References
Metrics cvssV3_1

{'score': 5.9, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
Mattermost
Published
Updated
Jul 15, 2026, 4:00 AM
Reserved
May 26, 2026, 11:52 AM
Status
Analyzed
Published
Jul 13, 2026, 9:16 AM
Modified
Jul 15, 2026, 5:17 AM