Affected: Gitea Open Source Git Server

Privilege Escalation via Access Token Scope Escalation in API

Affected: Go: code.gitea.io/gitea

Gitea's API endpoint for creating Personal Access Tokens (`POST /users/{username}/tokens`) is protected by a middleware (`reqBasicOrRevProxyAuth`) that is intended to require password-based authentication, preventing a compromised token from being used to mint new ones. However, when a token is passed in the `Authorization: Basic <token>:x-oauth-basic` format, the Basic auth handler validates it and sets `AuthedMethod="basic"`, causing `IsBasicAuth=true` and fooling the middleware into passing the request. Once past the guard, the token creation handler applies no scope ceiling — it will create a new token with any requested scope regardless of the caller's scope. An attacker with a restricted token (e.g. `write:user` from a leaked CI secret) can therefore create a fully-privileged `all`-scoped token without knowing the account password.

### Data flow

#### Step 1 - Token extracted from Basic auth header When the attacker sends Authorization: Basic base64(<token>:x-oauth-basic), parseAuthBasic detects that the password is "x-oauth-basic" and treats the username field as the token:

https://github.com/go-gitea/gitea/blob/9155a81b9daf1d46b2380aa91271e623ac947c1e/services/auth/basic.go#L55-L64

`VerifyAuthToken` then validates the token against the database and sets `LoginMethod = "access_token"` and `ApiTokenScope` to the token's actual scope (`write:user`):

https://github.com/go-gitea/gitea/blob/9155a81b9daf1d46b2380aa91271e623ac947c1e/services/auth/basic.go#L100-L106

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