{"id":"CVE-2021-4189","url":"https://www.cyber-defence.io/tools/cve/CVE-2021-4189","generatedAt":"2026-10-27T20:53:51.145Z","title":"This flaw allows an attacker to set up a malicious FTP server that can trick FTP clients into connecting back to a given IP address and port.","description":"A flaw was found in Python, specifically in the FTP (File Transfer Protocol) client library in PASV (passive) mode. The issue is how the FTP client trusts the host from the PASV response by default. This flaw allows an attacker to set up a malicious FTP server that can trick FTP clients into connecting back to a given IP address and port. This vulnerability could lead to FTP client scanning ports, which otherwise would not have been possible.","published":"2022-08-24T16:15:10.000Z","lastModified":"2026-10-14T11:16:55.000Z","status":"Modified","sourceIdentifier":"secalert@redhat.com","cvss":{"version":"3.1","score":5.3,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N"},"cwe":["CWE-252"],"affected":["python/python","debian/debian linux","redhat/software collections","redhat/enterprise linux","netapp/ontap select deploy administration utility"],"epss":{"score":0.03409,"percentile":0.88791,"date":"2026-10-26","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"low","text":"Lower severity and a low EPSS score (3.41%). Track it; it rarely justifies an emergency change on its own."},"changes":[],"references":[{"url":"https://access.redhat.com/security/cve/CVE-2021-4189","tags":["Third Party Advisory"],"source":"secalert@redhat.com"},{"url":"https://bugs.python.org/issue43285","tags":["Patch","Vendor Advisory"],"source":"secalert@redhat.com"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2036020","tags":["Issue Tracking","Patch","Third Party Advisory"],"source":"secalert@redhat.com"},{"url":"https://github.com/python/cpython/commit/0ab152c6b5d95caa2dc1a30fa96e10258b5f188e","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/ftplib-pasv.html","tags":["Patch","Third Party Advisory"],"source":"secalert@redhat.com"},{"url":"https://security-tracker.debian.org/tracker/CVE-2021-4189","tags":["Third Party Advisory"],"source":"secalert@redhat.com"},{"url":"https://security.netapp.com/advisory/ntap-20221104-0004/","tags":["Third Party Advisory"],"source":"secalert@redhat.com"},{"url":"https://access.redhat.com/security/cve/CVE-2021-4189","tags":["Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://bugs.python.org/issue43285","tags":["Patch","Vendor Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2036020","tags":["Issue Tracking","Patch","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://github.com/python/cpython/commit/0ab152c6b5d95caa2dc1a30fa96e10258b5f188e","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/2024/12/msg00000.html","source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://python-security.readthedocs.io/vuln/ftplib-pasv.html","tags":["Patch","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://security-tracker.debian.org/tracker/CVE-2021-4189","tags":["Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://security.netapp.com/advisory/ntap-20221104-0004/","tags":["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-2021-4189","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."}