Vulnerability Description
Mattermost versions 11.0.x <= 11.0.2, 10.12.x <= 10.12.1, 10.11.x <= 10.11.4, 10.5.x <= 10.5.12 fail to to verify that the token used during the code exchange originates from the same authentication flow, which allows an authenticated user to perform account takeover via a specially crafted email address used when switching authentication methods and sending a request to the /users/login/sso/code-exchange endpoint. The vulnerability requires ExperimentalEnableAuthenticationTransfer to be enabled (default: enabled) and RequireEmailVerification to be disabled (default: disabled).
CVSS Score
CRITICAL
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Mattermost | Mattermost Server | >= 10.5.0, < 10.5.13 |
Related Weaknesses (CWE)
References
- https://mattermost.com/security-updatesVendor Advisory
FAQ
What is CVE-2025-12421?
CVE-2025-12421 is a vulnerability with a CVSS score of 9.9 (CRITICAL). Mattermost versions 11.0.x <= 11.0.2, 10.12.x <= 10.12.1, 10.11.x <= 10.11.4, 10.5.x <= 10.5.12 fail to to verify that the token used during the code exchange originates from the same authentication f...
How severe is CVE-2025-12421?
CVE-2025-12421 has been rated CRITICAL with a CVSS base score of 9.9/10. This is considered a critical vulnerability requiring immediate attention.
Is there a patch for CVE-2025-12421?
Check the references section above for vendor advisories and patch information. Affected products include: Mattermost Mattermost Server.