{"id":"CVE-2021-3737","url":"https://www.cyber-defence.io/tools/cve/CVE-2021-3737","generatedAt":"2026-11-05T00:35:59.324Z","title":"An improperly handled HTTP response in the HTTP client code of python may allow a remote attacker, who controls the HTTP server, to make the client script enter an infinite loop, consuming CPU time.","description":"A flaw was found in python. An improperly handled HTTP response in the HTTP client code of python may allow a remote attacker, who controls the HTTP server, to make the client script enter an infinite loop, consuming CPU time. The highest threat from this vulnerability is to system availability.","published":"2022-03-04T19:15:09.000Z","lastModified":"2026-10-14T10:17:48.000Z","status":"Modified","sourceIdentifier":"secalert@redhat.com","cvss":{"version":"3.1","score":7.5,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},"cwe":["CWE-835","CWE-400"],"affected":["python/python","redhat/codeready linux builder","redhat/codeready linux builder for ibm z systems","redhat/codeready linux builder for power little endian","redhat/enterprise linux","redhat/enterprise linux for ibm z systems","redhat/enterprise linux for power little endian","fedoraproject/fedora","canonical/ubuntu linux","netapp/hci","netapp/management services for element software","netapp/netapp xcp smb","netapp/ontap select deploy administration utility","netapp/xcp nfs","oracle/communications cloud native core binding support function","oracle/communications cloud native core network exposure function","oracle/communications cloud native core policy"],"epss":{"score":0.13166,"percentile":0.96369,"date":"2026-11-03","history":[{"date":"2026-10-14","score":0.13166,"percentile":0.96315}]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"urgent","text":"EPSS puts the probability of exploitation in the next 30 days at 13.2%, higher than 96% of all known CVEs. Patch or mitigate before the next change window."},"changes":[],"references":[{"url":"https://bugs.python.org/issue44022","tags":["Exploit","Issue Tracking","Vendor Advisory"],"source":"secalert@redhat.com"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=1995162","tags":["Issue Tracking","Patch","Third Party Advisory"],"source":"secalert@redhat.com"},{"url":"https://github.com/python/cpython/pull/25916","tags":["Patch","Third Party Advisory"],"source":"secalert@redhat.com"},{"url":"https://github.com/python/cpython/pull/26503","tags":["Patch","Third Party Advisory"],"source":"secalert@redhat.com"},{"url":"https://lists.debian.org/debian-lts-announce/2023/05/msg00024.html","source":"secalert@redhat.com"},{"url":"https://lists.debian.org/debian-lts-announce/2023/06/msg00039.html","source":"secalert@redhat.com"},{"url":"https://python-security.readthedocs.io/vuln/urllib-100-continue-loop.html","tags":["Patch","Third Party Advisory"],"source":"secalert@redhat.com"},{"url":"https://security.netapp.com/advisory/ntap-20220407-0009/","tags":["Third Party Advisory"],"source":"secalert@redhat.com"},{"url":"https://ubuntu.com/security/CVE-2021-3737","tags":["Patch","Third Party Advisory"],"source":"secalert@redhat.com"},{"url":"https://www.oracle.com/security-alerts/cpujul2022.html","tags":["Patch","Third Party Advisory"],"source":"secalert@redhat.com"},{"url":"https://bugs.python.org/issue44022","tags":["Exploit","Issue Tracking","Vendor Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=1995162","tags":["Issue Tracking","Patch","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://github.com/python/cpython/pull/25916","tags":["Patch","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://github.com/python/cpython/pull/26503","tags":["Patch","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://lists.debian.org/debian-lts-announce/2023/05/msg00024.html","source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://lists.debian.org/debian-lts-announce/2023/06/msg00039.html","source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://lists.debian.org/debian-lts-announce/2024/11/msg00024.html","source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://lists.debian.org/debian-lts-announce/2024/12/msg00000.html","source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://python-security.readthedocs.io/vuln/urllib-100-continue-loop.html","tags":["Patch","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://security.netapp.com/advisory/ntap-20220407-0009/","tags":["Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://ubuntu.com/security/CVE-2021-3737","tags":["Patch","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://www.oracle.com/security-alerts/cpujul2022.html","tags":["Patch","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://cert-portal.siemens.com/productcert/html/ssa-398330.html","source":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2021-3737","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}