Mattermost versions 10.12.x <= 10.12.1, 10.11.x <= 10.11.4, 10.5.x <= 10.5.12, 11.0.x <= 11.0.3 fail to properly validate OAuth state tokens during OpenID Connect authentication which allows an authenticated attacker with team creation privileges to take over a user account via manipulation of authentication data during the OAuth completion flow. This requires email verification to be disabled (default: disabled), OAuth/OpenID Connect to be enabled, and the attacker to control two users in the SSO system with one of them never having logged into Mattermost.
The requirements for the product dictate the use of an established authentication algorithm, but the implementation of the algorithm is incorrect.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Mattermost_server | Mattermost | 10.5.0 (including) | 10.5.13 (excluding) |
| Mattermost_server | Mattermost | 10.11.0 (including) | 10.11.5 (excluding) |
| Mattermost_server | Mattermost | 10.12.0 (including) | 10.12.2 (excluding) |
| Mattermost_server | Mattermost | 11.0.0 (including) | 11.0.4 (excluding) |