CVE-2026-9571
Deactivated user accounts can continue to obtain valid OAuth access tokens via refresh token grant in Mattermost
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
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- High
- Privileges needed
- High
- User interaction
- None
What an attacker can affect
- Confidentiality
- High
- Integrity
- High
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
Deactivated user accounts can continue to obtain valid OAuth access tokens via refresh token grant in Mattermost
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
- Record
CVE-2026-9571- CVSS 3.1
- 5.9 Medium
CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:N - Weakness
- CWE-305
- Updated
- 2026-11-02
EUVDEUVD-2026-43305
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
- Record
EUVD-2026-43305- CVSS 3.1
- 5.9 Medium
CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:N - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-4v7j-4mvr-5975
Mattermost versions 11.7.x <= 11.7.2, 11.6.x <= 11.6.4, 10.11.x <= 10.11.19 fail to invalidate...
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
- Record
GHSA-4v7j-4mvr-5975- CVSS 3.1
- 5.9 Medium
CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:N - Weakness
- CWE-305
- Updated
- 2026-11-02
NVD
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
- Record
CVE-2026-9571- CVSS 3.1
- 5.9 Medium
CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:N - CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N - Weakness
- CWE-305
- Updated
- 2026-11-02
OSV
Deactivated user accounts can continue to obtain valid OAuth access tokens via refresh token grant in Mattermost
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
- Record
CVE-2026-9571- CVSS 3.1
- 5.9 Medium
CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:N - Weakness
- CWE-305
- Updated
- 2026-11-02
Affected products
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE List, EUVD, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-9571 is a medium vulnerability (CVSS 5.9) in Mattermost, published July 13, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.30%, the 23rd percentile. No source names a fixed version.