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OpenAdvisories
Medium · 5.9 CVE-2026-9571 EUVD-2026-43305GHSA-4v7j-4mvr-5975

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

Published Jul 13, 2026 · Updated Jul 15, 2026 · Assigned by Mattermost

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

Affected products

VendorProductAffectedFixed
Mattermost Mattermost 11.7.0 – ≤ 11.7.2, 11.6.0 – ≤ 11.6.4, 10.11.0 – ≤ 10.11.19 11.8.0

Advisories 1

References