CVE-2026-9571mediumCWE-305

CVE-2026-9571: medium-severity vulnerability in Mattermost

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

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13Vexday Risk Score

No sign of exploitation. No public exploitation artifact known so far.

ssvc Trackcvss 5.9epss 0.3%
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
CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:N
Affected products
Mattermost · Mattermost
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