{"id":"CVE-2026-49265","title":"OAuthLib is an implementation of the OAuth request-signing logic for Python 3.6+","summary":"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 …","severity":"medium","cvss":6.8,"cvssVector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N","cwe":["CWE-208"],"vendor":"oauthlib","product":"oauthlib","affected":["oauthlib >= 3.0.0, < 4.0.0"],"patched":["oauthlib 4.0.0"],"published":"2026-10-13","updated":"2026-10-16","sourceUpdated":"2026-10-16T20:04:29.760","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-49265","references":[{"url":"https://github.com/oauthlib/oauthlib/commit/74664d3fe037a354e180e305135c6bab1747a6b0","label":"security-advisories@github.com"},{"url":"https://github.com/oauthlib/oauthlib/pull/963","label":"security-advisories@github.com"},{"url":"https://github.com/oauthlib/oauthlib/releases/tag/v4.0.0","label":"security-advisories@github.com"},{"url":"https://github.com/oauthlib/oauthlib/security/advisories/GHSA-xpv3-w29h-x7cv","label":"security-advisories@github.com"},{"url":"https://github.com/pypa/advisory-database/tree/main/vulns/oauthlib/PYSEC-2026-4114.yaml","label":"security-advisories@github.com"},{"url":"https://github.com/oauthlib/oauthlib/commit/40b0ab56da3682c2484a4b78bbff309f8025d950"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-49265"},{"url":"https://github.com/advisories/GHSA-xpv3-w29h-x7cv"},{"url":"https://github.com/oauthlib/oauthlib"},{"url":"https://pypi.org/project/oauthlib"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-49265.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-49265"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2550336"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-49265"},{"url":"https://access.redhat.com/errata/RHSA-2026:82415"},{"url":"https://access.redhat.com/errata/RHSA-2026:82368"}],"tags":["nvd","ghsa","pip","osv","csaf","vex","red-hat","cve.org"],"epss":0.00242,"epssPercentile":0.15309,"aliases":["GHSA-xpv3-w29h-x7cv","PYSEC-2026-4114"],"ecosystem":"pip","ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"total","timestamp":"2026-10-13T16:19:32.600149Z"},"ingestedAt":"2026-09-29T18:42:35.834Z","slug":"CVE-2026-49265","body":"## Overview\n\nOAuthLib 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.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Package advisory (CVE-2026-49265)\n\nAffected packages:\n\n- `oauthlib >= 3.0.0, < 4.0.0`\n\nPatched in:\n\n- `oauthlib 4.0.0`\n\nSource: https://github.com/advisories/GHSA-xpv3-w29h-x7cv\n\n## Vendor advisories\n\n- **RHSA-2026:82415** · Red Hat · fixed in: Red Hat AI Inference Server 3.5 · released 2026-10-13 · [advisory](https://access.redhat.com/errata/RHSA-2026:82415)\n- **RHSA-2026:82368** · Red Hat · fixed in: Red Hat AI Inference Server 3.5 · released 2026-10-13 · [advisory](https://access.redhat.com/errata/RHSA-2026:82368)\n- **Red Hat VEX** · Moderate · affected: Confidential Compute Attestation, Fence Agents Remediation Operator, Lightspeed Core, Lightspeed Services for Advanced Cluster Management, Migration Toolkit for Applications 8, Migration Toolkit for Containers, … · no fix planned: Confidential Compute Attestation, Fence Agents Remediation Operator, Lightspeed Core, Lightspeed Services for Advanced Cluster Management, … · updated 2026-10-16 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-49265.json)","depth":"sunlit","depthScore":37,"depthScoreParts":{"impact":37.4,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}