OAuthLib is an implementation of the OAuth request-signing logic for Python 3.6+. From 3.0.0 until 4.0.0, OAuthLibs PKCE checks in oauthlib/oauth2/rfc6749/grant_types/authorization_code.py compare attacker-supplied code_verifier values with stored challenges using ordinary string equality in code_challenge_method_plain and code_challenge_method_s256. Because the comparison can return after a length difference or the first mismatching character, repeated token endpoint measurements can reveal common-prefix timing information that could potentially allow recovery of the code_verifier, unauthorized access-token acquisition, and account takeover. Practical exploitation requires an intercepted, single-use authorization code and enough measurements to overcome real-world network noise; the local timing benchmark does not establish practical remote account takeover, so the weakness remains a defense-in-depth concern. This issue is fixed in version 4.0.0.
Weakness
Two separate operations in a product require different amounts of time to complete, in a way that is observable to an actor and reveals security-relevant information about the state of the product, such as whether a particular operation was successful or not.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Red Hat AI Inference Server 3.5 | RedHat | rhaii/vllm-cuda-rhel9:1791473631 | * |
| Red Hat AI Inference Server 3.5 | RedHat | rhaii/vllm-cpu-rhel9:1791473614 | * |
| Red Hat Enterprise Linux AI 3.5 | RedHat | rhelai3/disk-image-cuda-rhel9:1793206758 | * |
| Red Hat Enterprise Linux AI 3.5 | RedHat | rhelai3/bootc-aws-cuda-rhel9:1793194817 | * |
| Red Hat Enterprise Linux AI 3.5 | RedHat | rhelai3/bootc-azure-cuda-rhel9:1793194815 | * |
| Red Hat Enterprise Linux AI 3.5 | RedHat | rhelai3/bootc-cuda-rhel9:1793135861 | * |
| Red Hat Enterprise Linux AI 3.5 | RedHat | rhelai3/bootc-gcp-cuda-rhel9:1793194815 | * |
Related Attack Patterns
- https://cwe.mitre.org/data/definitions/462.html
- https://cwe.mitre.org/data/definitions/541.html
- https://cwe.mitre.org/data/definitions/580.html
References
- https://github.com/oauthlib/oauthlib/commit/74664d3fe037a354e180e305135c6bab1747a6b0
- https://github.com/oauthlib/oauthlib/pull/963
- https://github.com/oauthlib/oauthlib/releases/tag/v4.0.0
- https://github.com/oauthlib/oauthlib/security/advisories/GHSA-xpv3-w29h-x7cv
- https://github.com/pypa/advisory-database/tree/main/vulns/oauthlib/PYSEC-2026-4114.yaml