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CVE-2021-4189

Published: Aug 24, 2022

Modified: Dec 17, 2025

PUBLISHED

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.

Vendor	Product	Versions
n/a	python	affected `Fixed in python 3.6.14, python 3.7.11, python 3.8.9, python 3.9.3, python 3.10.0`

References

https://bugs.python.org/issue43285

https://python-security.readthedocs.io/vuln/ftplib-pasv.html

https://github.com/python/cpython/commit/0ab152c6b5d95caa2dc1a30fa96e10258b5f188e

https://security-tracker.debian.org/tracker/CVE-2021-4189

https://bugzilla.redhat.com/show_bug.cgi?id=2036020

https://access.redhat.com/security/cve/CVE-2021-4189

https://security.netapp.com/advisory/ntap-20221104-0004/

[debian-lts-announce] 20230524 [SECURITY] [DLA 3432-1] python2.7 security update

mailing-list

[debian-lts-announce] 20230630 [SECURITY] [DLA 3477-1] python3.7 security update

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