CVE-2026-9571

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

State: Published
Severity: 5.9 Medium
Published: Jul 13, 2026
Updated: Jul 15, 2026
Reserved: May 26, 2026

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

Scores

CVSS	Score	Vector	Source
3.1	5.9 Medium	CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:N	Mattermost

Weaknesses

CWE-305 – Authentication Bypass by Primary Weakness

Affected Products

Product	Versions
MattermostMattermost	11.7.0 through 11.7.2Affected 11.6.0 through 11.6.4Affected 10.11.0 through 10.11.19Affected 11.8.0Not affected 11.7.3Not affected 11.6.5Not affected 10.11.20Not affected

References

MMSA-2026-00680vendor-advisory

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