Authlib: OpenID implicit grant checks raw scope instead of allowed scope before issuing ID tokens
- Published
- Last modified
- Status
- published
- Known exploitation
- Not listed in CISA KEV
- Public exploit
- None on Exploit-DB
Summary
Authlib, a Python library used to build OAuth and OpenID Connect servers, is affected. Servers before version 1.9.0 can issue ID tokens containing a user's identity information to clients that were not permitted the openid scope, though only when the implicit flow is used with an ID token response type.
Summarized by anthropic/claude-haiku-5.5. Verify details against the original sources.
Read the original description
Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to 1.9.0, OpenIDImplicitGrant.validate_authorization_request() checks the client-controlled raw request.payload.scope for openid after the parent grant has filtered allowed scopes into request.scope. A registered client permitted an ID token response type but not the openid scope can add openid to the request, obtain user consent, and receive a signed ID token containing the user's subject and allowed profile claims. Authorization code flow and deployments that allow openid for every client permitted an ID token response are not affected. In authlib/oidc/core/grants/implicit.py, OpenIDImplicitGrant.validate_authorization_request() checks request.payload.scope instead of the filtered request.scope. This issue is fixed in version 1.9.0.
Affected versions
- authlib authlib
fixed in 1.9.0