{"id":"CVE-2026-49265","revision":"7ac509df5f0c44d6b0c320d360184b56","records":[{"revision":"7ac509df5f0c44d6b0c320d360184b56","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-49265","aliases":[],"title":"OAuthLib: Timing Attack Vulnerability in PKCE code_verifier Comparison","description":"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.","state":0,"publishedAt":"2026-10-13T15:47:11.854+00:00","modifiedAt":"2026-10-13T16:19:39.092+00:00","affected":[{"ecosystem":"Vendor product","name":"oauthlib","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"vendor\": \"oauthlib\",\n                    \"product\": \"oauthlib\",\n                    \"versions\": [\n                        {\n                            \"version\": \">= 3.0.0, < 4.0.0\",\n                            \"status\": \"affected\"\n                        }\n                    ]\n                }"}],"metrics":[{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N","score":6.8,"severity":"MEDIUM"}],"references":["https://github.com/oauthlib/oauthlib/security/advisories/GHSA-xpv3-w29h-x7cv","https://github.com/oauthlib/oauthlib/pull/963","https://github.com/oauthlib/oauthlib/commit/74664d3fe037a354e180e305135c6bab1747a6b0","https://github.com/oauthlib/oauthlib/releases/tag/v4.0.0","https://github.com/pypa/advisory-database/tree/main/vulns/oauthlib/PYSEC-2026-4114.yaml"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-49265","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-49265","identifiers":["CVE-2026-49265"]},"retained":false,"historicalAffected":[]}],"coverage":[]}