Oauthlib: Timing Attack Vulnerability in PKCE code_verifier Comparison (CWE-208) — GHSA-XPV3-W29H-X7CV

Summary

## Summary A timing side-channel vulnerability exists in the PKCE (RFC 7636) implementation of the Authorization Code Grant flow. The `code_challenge_method_plain` function uses Python's standard `==` operator for string comparison instead of a constant-time comparison function, potentially allowing timing-based attacks. ## Affected Component - File: `oauthlib/oauth2/rfc6749/grant_types/authorization_code.py` -…

Timeline

Published by source

2026-09-29

Risk context

• Reported severity or threat level: medium.
• Reported CVSS score: 6.8 out of 10.
• Review exposure for the affected product or family: pip: oauthlib.

Product

pip: oauthlib

What to do

General, cautious steps (verify details in the official source):

• Review exposure and plan remediation based on risk and environment.
• Identify affected product versions in your inventory and verify whether you are impacted.
• Apply vendor patches/updates or recommended mitigations as soon as available.
• Read the official advisory for exact affected versions and remediation steps.

Official advisory

• Read the official source
• CVE Record
• NVD

Evidence and provenance

Canonical advisory ID

GHSA-XPV3-W29H-X7CV

Source

GitHub

Vendor

GitHub

Published by source

2026-09-29

Last source activity

2026-09-29

Additional identifiers

CVE-2026-49265

Curated by

hlukh.ch

Related advisories and connections

These advisories are connected by shared CVE, product, vendor, source, or time signals.