Medium severity · published Jul 13, 2026
CVE-2026-9571
Deactivated user accounts can continue to obtain valid OAuth access tokens via refresh token grant in Mattermost
6.5
CVSS
0.3%
EPSS
No
On KEV
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
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Confidentiality
High
Integrity
None
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 23% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
MA
Mattermost · Mattermost
11.7.0 through 11.7.2; 11.6.0 through 11.6.4; 10.11.0 through 10.11.19 · source: vendor
MS
Mattermost Server · Mattermost
10.11.0 before 10.11.20; 11.6.0 before 11.6.5; 11.7.0 before 11.7.3 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-9571
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-9571
Vendor Advisory
https://mattermost.com/security-updates
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