Headline
GHSA-mp6x-97xj-9x62: Mattermost fails to to verify the token used during code exchange
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).
- GitHub Advisory Database
- GitHub Reviewed
- CVE-2025-12421
Mattermost fails to to verify the token used during code exchange
Critical severity GitHub Reviewed Published Nov 27, 2025 to the GitHub Advisory Database • Updated Dec 1, 2025
Package
gomod github.com/mattermost/mattermost-server (Go)
Affected versions
>= 11.0.0, < 11.0.3
>= 10.12.0, < 10.12.2
>= 10.11.0, < 10.11.5
>= 10.5.0, < 10.5.13
Patched versions
11.0.3
10.12.2
10.11.5
10.5.13
gomod github.com/mattermost/mattermost/server/v8 (Go)
< 8.0.0-20251022210333-acda1fb5dd46
8.0.0-20251022210333-acda1fb5dd46
Published to the GitHub Advisory Database
Nov 27, 2025