Medium 5.3Published Aug 23, 2022

CVE-2021-4189A flaw was found in Python, specifically in the FTP (File Transfer Protocol) client library in PASV (passive) mode.

Updated under an hour ago (Oct 26, 2026, 2:50 PM ET)

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It affects Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP and 7 other products. Add what you run to find out whether that includes you.

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Every CVE for Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP

Exploited in the last 30 days

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: 5.3 MEDIUM (v3.1, CISA ADP)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Weakness (CWE): CWE-252
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: redhat
NVD analysis: Modified
Record last updated: Oct 14, 2026
First seen by InfoSec Signals: Oct 14, 2026

Affected products

Affected products

Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP siemens:simatic_s7_1500_cpu_1518_4_pn_dp_mfp (from the name)	from V3.1.0 before V3.1.5	CISA ADP
Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP siemens:simatic_s7_1500_cpu_1518f_4_pn_dp_mfp (from the name)	from V3.1.0 before V3.1.5	CISA ADP
Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP siemens:siplus_s7_1500_cpu_1518_4_pn_dp_mfp (from the name)	from V3.1.0 before V3.1.5	CISA ADP
python python python:python	from 3.6.0 before 3.6.14; from 3.7.0 before 3.7.11; from 3.8.0 before 3.8.9; from 3.9.0 before 3.9.3; 3.10.0	NVD
debian debian_linux debian:debian_linux	10.0; 11.0	NVD
redhat software_collections redhat:software_collections	all versions	NVD
redhat enterprise_linux redhat:enterprise_linux	8.0	NVD
netapp ontap_select_deploy_administration_utility netapp:ontap_select_deploy_administration_utility	all versions	NVD

References

References

https://bugs.python.org/issue43285	patch, vendor-advisory
https://python-security.readthedocs.io/vuln/ftplib-pasv.html	patch, third-party-advisory
https://github.com/python/cpython/commit/0ab152c6b5d95caa2dc1a30fa96e10258b5f188e	patch, third-party-advisory
https://security-tracker.debian.org/tracker/CVE-2021-4189	third-party-advisory
https://bugzilla.redhat.com/show_bug.cgi?id=2036020	issue-tracking, patch, third-party-advisory
https://access.redhat.com/security/cve/CVE-2021-4189	third-party-advisory
https://security.netapp.com/advisory/ntap-20221104-0004/	third-party-advisory
https://lists.debian.org/debian-lts-announce/2023/05/msg00024.html	mailing-list
https://lists.debian.org/debian-lts-announce/2023/06/msg00039.html	mailing-list
https://lists.debian.org/debian-lts-announce/2024/12/msg00000.html
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The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.