CVE-2026-9571 json
Deactivated user accounts can continue to obtain valid OAuth access tokens via refresh token grant in Mattermost
published 2026-07-13 3 mo ago modified 2026-07-15 3 mo ago also EUVD-2026-43305
- cvss
- 5.9
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.3%
- EPSS 0.3% chance of exploitation in 30 days, percentile 23%
- public exploits
- 0
- none known
Summary
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
Patch / fix
- Mattermost Mattermost 10.11.20, 11.6.5, 11.7.3, 11.8.0
CISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- total
- Assessed
- 3 mo ago
Exploit prediction
0.30% chance of exploitation in the next 30 days, higher than 23% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 5.9 | CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:N |
| NVD | 3.1 | 6.5 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N |
Affected products
- Mattermost Mattermost
Classification
- Weakness
-
- CWE-305 Authentication Bypass by Primary Weakness
References
-
mattermost.com
/security-updates
vendor-advisory
Sources
- CVE List CVE-2026-9571
- NVD CVE-2026-9571
Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.