OAuthLib is an implementation of the OAuth request-signing logic for Python 3.6+. In OAuthLib versions 3.1.1 until 3.2.1, an attacker providing malicious redirect uri can cause denial of service. An attacker can also leverage usage of `uri_validate` functions depending where it is used. OAuthLib applications using OAuth2.0 provider support or use directly `uri_validate` are affected by this issue. Version 3.2.1 contains a patch. There are no known workarounds.
#### Mitigation

The redirect_uri can be verified in web toolkit before OAuthLib is called. A sample check if : is present to reject the request can prevent the denial of service, assuming no port or IPv6 is fundamentally required.Read More