CVE-2025-12421
9.9 · CRITICALOverview
CVE-2025-12421 is a critical-severity vulnerability affecting mattermost mattermost_server. It was published on November 27, 2025 and has a CVSS 3.1 base score of 9.9 (CRITICAL).
This vulnerability has a CVSS 3.1 base score of 9.9, rated CRITICAL. It can be exploited remotely over the network. Some level of privileges is required for exploitation.
Technical 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).
Remediation
Check the references section for vendor advisories and patches from mattermost. Update mattermost_server to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
Affected Products
| Vendor | Product | Versions | Status |
|---|---|---|---|
| mattermost | mattermost_server | >= 10.5.0, < 10.5.13 | Affected |
References
Frequently Asked Questions
What is CVE-2025-12421?
CVE-2025-12421 is a critical-severity vulnerability affecting mattermost mattermost_server. It was published on November 27, 2025 and has a CVSS 3.1 base score of 9.9 (CRITICAL).
How severe is CVE-2025-12421?
This vulnerability has a CVSS 3.1 base score of 9.9, rated CRITICAL. It can be exploited remotely over the network. Some level of privileges is required for exploitation.
How do I fix or remediate CVE-2025-12421?
Check the references section for vendor advisories and patches from mattermost. Update mattermost_server to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
How can CyberStrike help with CVE-2025-12421?
CyberStrike's AI-powered security agents can automatically detect CVE-2025-12421 across your infrastructure using autonomous pentesting, DAST scanning, and HackBrowser. The platform continuously monitors for known vulnerabilities and provides actionable remediation guidance prioritized by real-world exploitability.
How CyberStrike Helps
AI agents map your attack surface to find vulnerabilities like this one.
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