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CVE-2021-4189

Published: Aug 24, 2022Updated: Dec 17, 2025 Sources: CVE List NVD BDU csafCWE-252
NVD MITRE
5.3CVSSMEDIUM
EPSS Score
2.4%
Top 18.2%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available

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.

CVSS Vector Breakdown

AV:NAC:LPR:NUI:NS:UC:LI:NA:N
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:LConfidentiality
Low
I:NIntegrity
None
A:NAvailability
None
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Weaknesses

CWE-252

Affected Products

pythonn/a
pythonpythonOSS Libraries
debian linuxdebian
On-premOS
Operating Systems / linux-distro
software collectionsredhat
On-prem
DevTools & CI / build-test-tools
enterprise linuxredhat
On-premOS
Operating Systems / linux-distro
pythonoss-projectUSOSS Libraries
debianoss-projectGBOperating Systemsaka debian gnu/linux
redhatcommercialUSOperating Systemsaka red hat
and 11 more affected products View all →

Exploitability

Official Patch Available

References

https://bugs.python.org/issue43285
bugs.python.org
https://python-security.readthedocs.io/vuln/ftplib-pasv.html
python-security.readthedocs.io
https://github.com/python/cpython/commit/0ab152c6b5d95caa2dc1a30fa96e10258b5f188e
github.com
and 33 more references View all →

Timeline

Published
Aug 24, 2022
Last Updated
Dec 17, 2025

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