Critical Vulnerability in Mattermost Allows Account Takeover (CVE-2025-12421)
Mattermost Critical Vulnerability Summary A default configuration in Mattermost, an open source collaboration platform used by enterprises and government agencies, exposes deployments to critical Account Takeover risk. The vulnerability, identified as CVE-2025-12421, allows an attacker, via a single request, to hijack any user account on the system. Technical Details of CVE-2025-12421 The flaw lies in Mattermost’s authentication flow, specifically its handling of switching between different authentication methods (such as email/password to OAuth). The problem is in the /users/login/sso/code-exchange endpoint. ...