OAuthLib vulnerabilities

Prior to 4.0.0, OAuthLib's client_credentials and Resource Owner Password Credentials token grant handlers can authenticate request.client as one confidential client while retaining an attacker-supplied request.client_id for validate_grant_type and validate_scopes. A lower-privilege authenticated client can therefore cause grant and scope authorization to use another client's identity, potentially issuing tokens with unauthorized grants or scopes.

OAuthLib versions 3.0.0 through 4.0.0 compare attacker-supplied code_verifier values with stored challenges using ordinary string equality in PKCE checks, potentially leaking common-prefix timing information. This could allow recovery of the code_verifier, unauthorized access-token acquisition, and account takeover, though practical exploitation requires an intercepted single-use authorization code and many measurements. The issue is fixed in version 4.0.0.

OAuthLib versions 0.6.1 through 4.0.0, when enable_jsonp=True, reflect an unvalidated callback request parameter into success and error response bodies in RevocationEndpoint. This allows execution of attacker-controlled JavaScript in the context of an application that loads the response as trusted JSONP, if the attacker can influence the callback. The feature is disabled by default and only affects deployments that explicitly enable JSONP. Fixed in version 4.0.0.