{"id":"UBUNTU-CVE-2021-3733","details":"There's a flaw in urllib's AbstractBasicAuthHandler class. An attacker who controls a malicious HTTP server that an HTTP client (such as web browser) connects to, could trigger a Regular Expression Denial of Service (ReDOS) during an authentication request with a specially crafted payload that is sent by the server to the client. The greatest threat that this flaw poses is to application availability.","modified":"2026-04-22T14:52:44.442457Z","published":"2021-09-02T00:00:00Z","related":["USN-5083-1","USN-5199-1","USN-5200-1","USN-6891-1"],"upstream":["CVE-2021-3733"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2021-3733"},{"type":"REPORT","url":"https://bugs.python.org/issue43075"},{"type":"REPORT","url":"https://github.com/python/cpython/pull/24391"},{"type":"REPORT","url":"https://github.com/python/cpython/commit/7215d1ae25525c92b026166f9d5cac85fb1defe1"},{"type":"REPORT","url":"https://github.com/python/cpython/commit/a21d4fbd549ec9685068a113660553d7f80d9b09"},{"type":"REPORT","url":"https://github.com/python/cpython/commit/e7654b6046090914a8323931ed759a94a5f85d60"},{"type":"REPORT","url":"https://github.com/python/cpython/commit/ada14995870abddc277addf57dd690a2af04c2da"},{"type":"REPORT","url":"https://github.com/python/cpython/commit/3fbe96123aeb66664fa547a8f6022efa2dc8788f"},{"type":"ADVISORY","url":"https://ubuntu.com/security/notices/USN-5083-1"},{"type":"ADVISORY","url":"https://ubuntu.com/security/notices/USN-5199-1"},{"type":"ADVISORY","url":"https://ubuntu.com/security/notices/USN-5200-1"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2021-3733"},{"type":"ADVISORY","url":"https://ubuntu.com/security/notices/USN-6891-1"}],"affected":[{"package":{"name":"python3.4","ecosystem":"Ubuntu:Pro:14.04:LTS","purl":"pkg:deb/ubuntu/python3.4@3.4.3-1ubuntu1~14.04.7+esm11?arch=source&distro=trusty/esm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.4.3-1ubuntu1~14.04.7+esm11"}]}],"versions":["3.4~b1-0ubuntu3","3.4~b1-4ubuntu4","3.4~b1-4ubuntu6","3.4~b1-5ubuntu2","3.4~b2-1","3.4~b3-1ubuntu1","3.4~rc1-1build1","3.4~rc2-1","3.4~rc3-0ubuntu1","3.4.0-1","3.4.0-2ubuntu1","3.4.0-2ubuntu1.1","3.4.3-1ubuntu1~14.04.1","3.4.3-1ubuntu1~14.04.3","3.4.3-1ubuntu1~14.04.4","3.4.3-1ubuntu1~14.04.5","3.4.3-1ubuntu1~14.04.6","3.4.3-1ubuntu1~14.04.7","3.4.3-1ubuntu1~14.04.7+esm2","3.4.3-1ubuntu1~14.04.7+esm4","3.4.3-1ubuntu1~14.04.7+esm6","3.4.3-1ubuntu1~14.04.7+esm7","3.4.3-1ubuntu1~14.04.7+esm8","3.4.3-1ubuntu1~14.04.7+esm10"],"ecosystem_specific":{"availability":"Available 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