{"id":"UBUNTU-CVE-2021-33503","details":"An issue was discovered in urllib3 before 1.26.5. When provided with a URL containing many @ characters in the authority component, the authority regular expression exhibits catastrophic backtracking, causing a denial of service if a URL were passed as a parameter or redirected to via an HTTP redirect.","modified":"2026-02-04T02:15:25.333429Z","published":"2021-06-29T11:15:00Z","related":["USN-5812-1"],"upstream":["CVE-2021-33503"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2021-33503"},{"type":"REPORT","url":"https://github.com/advisories/GHSA-q2q7-5pp4-w6pg"},{"type":"REPORT","url":"https://github.com/urllib3/urllib3/commit/2d4a3fee6de2fa45eb82169361918f759269b4ec"},{"type":"ADVISORY","url":"https://ubuntu.com/security/notices/USN-5812-1"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2021-33503"}],"affected":[{"package":{"name":"python-pip","ecosystem":"Ubuntu:20.04:LTS","purl":"pkg:deb/ubuntu/python-pip@20.0.2-5ubuntu1.7?arch=source&distro=focal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"20.0.2-5ubuntu1.7"}]}],"versions":["18.1-5","18.1-5build1","18.1-5ubuntu1","20.0.2-2","20.0.2-4","20.0.2-5","20.0.2-5ubuntu1","20.0.2-5ubuntu1.1","20.0.2-5ubuntu1.3","20.0.2-5ubuntu1.4","20.0.2-5ubuntu1.5","20.0.2-5ubuntu1.6"],"ecosystem_specific":{"binaries":[{"binary_name":"python-pip-whl","binary_version":"20.0.2-5ubuntu1.7"},{"binary_name":"python3-pip","binary_version":"20.0.2-5ubuntu1.7"}],"availability":"No subscription required"},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-33503.json"}},{"package":{"name":"python-urllib3","ecosystem":"Ubuntu:20.04:LTS","purl":"pkg:deb/ubuntu/python-urllib3@1.25.8-2ubuntu0.2?arch=source&distro=focal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.25.8-2ubuntu0.2"}]}],"versions":["1.24.1-1ubuntu1","1.24.1-1ubuntu2","1.25.8-1","1.25.8-2","1.25.8-2ubuntu0.1"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-urllib3","binary_version":"1.25.8-2ubuntu0.2"}],"availability":"No subscription required"},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-33503.json"}}],"schema_version":"1.7.3","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},{"type":"Ubuntu","score":"low"}]}