Timing Attack Affecting oauthlib package, versions [3.0.0,4.0.0)
Threat Intelligence
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-PYTHON-OAUTHLIB-20305255
- published30 Sept 2026
- disclosed29 Sept 2026
- creditElvin Latifli
Introduced: 29 Sep 2026
NewCVE-2026-49265 (opens in a new tab)How to fix?
Upgrade oauthlib to version 4.0.0 or higher.
Overview
Affected versions of this package are vulnerable to Timing Attack via the code_challenge_method_s256 and code_challenge_method_plain functions in oauthlib/oauth2/rfc6749/grant_types/authorization_code.py, which compare PKCE code verifiers and challenges using the non-constant-time == operator. An attacker can exploit the resulting timing side-channel to progressively recover a valid PKCE code verifier or challenge through repeated token-endpoint requests, ultimately bypassing the PKCE authorization code binding and gaining unauthorized access to protected resources.