CVE-2026-9571 — Deactivated user accounts can continue to obtain valid OAuth access tokens via refresh token grant in Mattermost

CVE-2026-9571

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

Description (CNA)

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

Affected (CNA)

Vendor / product	Versions
Mattermost / Mattermost	affected 11.7.0 through 11.7.2; affected 11.6.0 through 11.6.4; affected 10.11.0 through 10.11.19; unaffected 11.8.0; unaffected 11.7.3; unaffected 11.6.5; unaffected 10.11.20

CWE

CWE-305

References

https://mattermost.com/security-updates

ADP enrichment

CISA-ADP

No English description supplied.

No references supplied.