{"id":"UBUNTU-CVE-2026-49265","details":"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.","modified":"2026-10-17T12:58:33.137980060Z","published":"2026-10-13T16:17:00Z","upstream":["CVE-2026-49265"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-49265"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-49265"},{"type":"REPORT","url":"https://github.com/oauthlib/oauthlib/commit/74664d3fe037a354e180e305135c6bab1747a6b0"},{"type":"REPORT","url":"https://github.com/oauthlib/oauthlib/pull/963"},{"type":"REPORT","url":"https://github.com/oauthlib/oauthlib/releases/tag/v4.0.0"},{"type":"REPORT","url":"https://github.com/oauthlib/oauthlib/security/advisories/GHSA-xpv3-w29h-x7cv"},{"type":"REPORT","url":"https://github.com/pypa/advisory-database/tree/main/vulns/oauthlib/PYSEC-2026-4114.yaml"}],"affected":[{"package":{"name":"python-oauthlib","ecosystem":"Ubuntu:16.04:LTS","purl":"pkg:deb/ubuntu/python-oauthlib?arch=source&distro=xenial"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.0.0-1","1.0.3-1"],"ecosystem_specific":{"binaries":[{"binary_version":"1.0.3-1","binary_name":"python-oauthlib"},{"binary_name":"python3-oauthlib","binary_version":"1.0.3-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-49265.json"}},{"package":{"name":"python-oauthlib","ecosystem":"Ubuntu:18.04:LTS","purl":"pkg:deb/ubuntu/python-oauthlib?arch=source&distro=bionic"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.0.1-1","2.0.4-1","2.0.6-1"],"ecosystem_specific":{"binaries":[{"binary_name":"python-oauthlib","binary_version":"2.0.6-1"},{"binary_name":"python3-oauthlib","binary_version":"2.0.6-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-49265.json"}},{"package":{"name":"python-oauthlib","ecosystem":"Ubuntu:20.04:LTS","purl":"pkg:deb/ubuntu/python-oauthlib?arch=source&distro=focal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.1.0-1","3.1.0-1ubuntu1","3.1.0-1ubuntu2"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-oauthlib","binary_version":"3.1.0-1ubuntu2"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-49265.json"}},{"package":{"name":"python-oauthlib","ecosystem":"Ubuntu:22.04:LTS","purl":"pkg:deb/ubuntu/python-oauthlib?arch=source&distro=jammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.1.0-2","3.1.1-1","3.2.0-1","3.2.0-1ubuntu0.1"],"ecosystem_specific":{"binaries":[{"binary_version":"3.2.0-1ubuntu0.1","binary_name":"python3-oauthlib"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-49265.json"}},{"package":{"name":"python-oauthlib","ecosystem":"Ubuntu:24.04:LTS","purl":"pkg:deb/ubuntu/python-oauthlib?arch=source&distro=noble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.2.2-1"],"ecosystem_specific":{"binaries":[{"binary_version":"3.2.2-1","binary_name":"python3-oauthlib"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-49265.json"}},{"package":{"name":"python-oauthlib","ecosystem":"Ubuntu:26.10","purl":"pkg:deb/ubuntu/python-oauthlib?arch=source&distro=stonking"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.3.1-1build1","3.3.1-2"],"ecosystem_specific":{"binaries":[{"binary_version":"3.3.1-2","binary_name":"python3-oauthlib"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-49265.json"}},{"package":{"name":"python-oauthlib","ecosystem":"Ubuntu:26.04:LTS","purl":"pkg:deb/ubuntu/python-oauthlib?arch=source&distro=resolute"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.2.2-3","3.3.1-1","3.3.1-1build1"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-oauthlib","binary_version":"3.3.1-1build1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-49265.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N"},{"type":"Ubuntu","score":"medium"}]}