Description

OAuthLib vulnerable to DoS when attacker provides malicious IPV6 URI

Impact

Attacker providing malicious redirect uri can cause DoS to oauthlib's web application.

Attacker can also leverage usage of uri_validate functions depending where it is used.

What kind of vulnerability is it? Who is impacted?

Oauthlib applications using OAuth2.0 provider support or use directly uri_validate function.

Patches

Has the problem been patched? What versions should users upgrade to?

Issue fixed in 3.2.2 release.

Workarounds

Is there a way for users to fix or remediate the vulnerability without upgrading?

The redirect_uri can be verified in web toolkit (i.e bottle-oauthlib, django-oauth-toolkit, ...) before oauthlib is called. A sample check if : is present to reject the request can prevent the DoS, assuming no port or IPv6 is fundamentally required.

References

Attack Vector:

Attacker providing malicious redirect uri: https://github.com/oauthlib/oauthlib/blob/d4bafd9f1d0eba3766e933b1ac598cbbf37b8914/oauthlib/oauth2/rfc6749/grant_types/base.py#L232

Vulnerable uri_validate functions: https://github.com/oauthlib/oauthlib/blob/2b8a44855a51ad5a5b0c348a08c2564a2e197ea2/oauthlib/uri_validate.py

PoC

is_absolute_uri("http://[:::::::::::::::::::::::::::::::::::::::]/path")

Acknowledgement

Special thanks to Sebastian Chnelik - PyUp.io

Mitigation

Aliases

References