Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13 fail to enforce client identity binding during the OAuth authorization code redemption flow which allows an authenticated OAuth client to redeem authorization codes issued to a different client via a crafted token exchange request.. Mattermost Advisory ID: MMSA-2026-00570
Weakness
The authentication algorithm is sound, but the implemented mechanism can be bypassed as the result of a separate weakness that is primary to the authentication error.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Mattermost_server | Mattermost | 10.11.0 (including) | 10.11.14 (excluding) |
| Mattermost_server | Mattermost | 11.5.0 (including) | 11.5.2 (excluding) |