HOMEVULNERABILITIESCVE-2021-4189
MEDIUM

CVE-2021-4189

CWE-252Published: August 24, 2022· Updated: Jun 17, 2026

5.3
CVSS v3.1

Official 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.

NVD Source

Technical Analysis

CVE-2021-4189 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

CVSS v3.1 Vector Breakdown

Exploitability
Attack VectorNetwork
Attack ComplexityLow
Privileges Req.None
User InteractionNone
ScopeUnchanged
Impact
ConfidentialityLow
IntegrityNone
AvailabilityNone
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Affected Vendors & Products

Debian1 product(s)
debian linux
netapp1 product(s)
ontap select deploy administration utility
Python1 product(s)
python
Red Hat2 product(s)
software collectionsenterprise linux
Source: NVD CPE · 7 total CPE entries

Exploit & PoC Resources

NO KNOWN EXPLOITNo public exploit confirmed at this time
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
External links open in a new tab. Always verify in a controlled environment before use.

Official Patches & Advisories

PATCHhttps://bugs.python.org/issue43285
PATCHhttps://bugzilla.redhat.com/show_bug.cgi?id=2036020
PATCHhttps://github.com/python/cpython/commit/0ab152c6b5d95caa2dc1a30fa96e10258b5f188e
PATCHhttps://python-security.readthedocs.io/vuln/ftplib-pasv.html
PATCHhttps://bugs.python.org/issue43285
PATCHhttps://bugzilla.redhat.com/show_bug.cgi?id=2036020
PATCHhttps://github.com/python/cpython/commit/0ab152c6b5d95caa2dc1a30fa96e10258b5f188e
PATCHhttps://python-security.readthedocs.io/vuln/ftplib-pasv.html
ADVISORYhttps://access.redhat.com/security/cve/CVE-2021-4189
ADVISORYhttps://security-tracker.debian.org/tracker/CVE-2021-4189
ADVISORYhttps://security.netapp.com/advisory/ntap-20221104-0004/
ADVISORYhttps://access.redhat.com/security/cve/CVE-2021-4189
ADVISORYhttps://security-tracker.debian.org/tracker/CVE-2021-4189
ADVISORYhttps://security.netapp.com/advisory/ntap-20221104-0004/

All References (19)

→
https://access.redhat.com/security/cve/CVE-2021-4189Third Party Advisory
→
https://bugs.python.org/issue43285Patch · Vendor Advisory
→
https://bugzilla.redhat.com/show_bug.cgi?id=2036020Issue Tracking · Patch · Third Party Advisory
→
https://github.com/python/cpython/commit/0ab152c6b5d95caa2dc1a30fa96e10258b5f188ePatch · Third Party Advisory
→
https://lists.debian.org/debian-lts-announce/2023/05/msg00024.html
→
https://lists.debian.org/debian-lts-announce/2023/06/msg00039.html
→
https://python-security.readthedocs.io/vuln/ftplib-pasv.htmlPatch · Third Party Advisory
→
https://security-tracker.debian.org/tracker/CVE-2021-4189Third Party Advisory
→
https://security.netapp.com/advisory/ntap-20221104-0004/Third Party Advisory
→
https://access.redhat.com/security/cve/CVE-2021-4189Third Party Advisory
→
https://bugs.python.org/issue43285Patch · Vendor Advisory
→
https://bugzilla.redhat.com/show_bug.cgi?id=2036020Issue Tracking · Patch · Third Party Advisory
→
https://github.com/python/cpython/commit/0ab152c6b5d95caa2dc1a30fa96e10258b5f188ePatch · Third Party Advisory
→
https://lists.debian.org/debian-lts-announce/2023/05/msg00024.html
→
https://lists.debian.org/debian-lts-announce/2023/06/msg00039.html

Quick Facts

CVE IDCVE-2021-4189
CVSS Score5.3 / 10
SeverityMEDIUM
WeaknessCWE-252
CISA KEVNo
Affected4 vendor(s)
PublishedAug 24, 2022

Related CVEs (CWE-252)

CVE-2007-3798
9.8
CVE-2019-15900
9.8
CVE-2010-0211
9.8
CVE-2025-66565
9.8
CVE-2021-38171
9.8
CVE-2022-25718
9.8

Recommended Actions

  • →Apply vendor patches immediately
  • →Monitor CVE-2021-4189 in threat intel feeds
  • →Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWatch. CVE data is provided under the NVD usage policy.
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