Answer in brief
CVE-2026-49265 records a Medium severity (CVSS 6.8) vulnerability in OAuthLib: Timing Attack Vulnerability in PKCE code_verifier Comparison. The current sources do not mark it as known exploited. The current feed maps oauthlib/oauthlib (generic), oauthlib (pip), oauthlib (pypi). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 6.8. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps oauthlib/oauthlib (generic), oauthlib (pip), oauthlib (pypi). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| oauthlib/oauthlibgeneric | >=3.0.0 <4.0.0 | 4.0.0 |
| oauthlibpip | >=3.0.0,<4.0.0 | 4.0.0 |
| oauthlibpypi | >=3.0.0 <4.0.0 | 4.0.0 |
Published upstream
Oct 13, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Oct 16, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Sep 29, 2026
OAuthLib is an implementation of the OAuth request-signing logic for Python 3.6+. From 3.0.0 until 4.0.0, OAuthLib's 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.
Quoted source text, attributed separately from HOL analysis.