No exploitation reportedFix available

CVE-2021-4189

Q: Is CVE-2021-4189 actively exploited?

Active exploitation of CVE-2021-4189 has not been confirmed. Its EPSS score was 3.4% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

Q: What is the CVSS score for CVE-2021-4189?

CVE-2021-4189 has a CVSS v3 base score of 5.3 (MEDIUM severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N.

No exploitation reported by the sources we read.

Published2022-08-24
Fixed in3.10.1 · 3.9.3 · 3.8.9 · 3.7.11 · 3.6.14
WeaknessCWE-252

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

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.

Timeline

dates in UTC

2022-08-2416:15CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-4189?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-4189?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

OSV · NVD

Python

Branch	Affected	Fixed in	Source
3.10	≥ 3.10.0, < 3.10.1	3.10.1	OSV
3.9	≥ 3.9.0, < 3.9.3	3.9.3	NVD · OSV
3.8	≥ 3.8.0, < 3.8.9	3.8.9	NVD · OSV
3.7	≥ 3.7.0, < 3.7.11	3.7.11	NVD · OSV
3.6	≥ 3.6.0, < 3.6.14	3.6.14	NVD · OSV
3.10	= 3.10.0	no fix published	NVD

Debian debian linux

Branch	Affected	Fixed in	Source
10.0	= 10.0	no fix published	NVD
11.0	= 11.0	no fix published	NVD

Netapp ontap select deploy administration utility

Branch	Affected	Fixed in	Source
—	all versions	no fix published	NVD

2 more products in the sources.

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

babelAlmaLinux:8all versions · fixed in 2.5.1-10.module_el8.6.0+2781+fed64c13and 1 other package
platform-pythonAlmaLinux:8all versions · fixed in 3.6.8-45.el8.almaand 6 other packages
python-nose-docsAlmaLinux:8all versions · fixed in 1.3.7-31.module_el8.5.0+2569+5c5719bc
python-sqlalchemy-docAlmaLinux:8all versions · fixed in 1.3.2-2.module_el8.5.0+2569+5c5719bc
python2AlmaLinux:8all versions · fixed in 2.7.18-10.module_el8.6.0+2781+fed64c13.almaand 6 other packages
python2-attrsAlmaLinux:8all versions · fixed in 17.4.0-10.module_el8.6.0+2781+fed64c13
python2-backportsAlmaLinux:8all versions · fixed in 1.0-16.module_el8.6.0+2781+fed64c13
python2-backports-ssl_match_hostnameAlmaLinux:8all versions · fixed in 3.5.0.1-12.module_el8.6.0+2781+fed64c13

37 more package ranges on OSV.dev

Full record on NVD

Fix

Update Python to 3.10.1 · 3.9.3 · 3.8.9 · 3.7.11 · 3.6.14

Advisories and patches

Detection

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: none listed

Sources

CISA-ADPSSVC decisionnone2025-06-25
OpenCVESSVC decisionnone—
CISA-ADPCVSS 3.15.32025-06-25
NVDCVSS 3.15.3read 2026-10-23
CISA-ADPweakness (CWE)CWE-2522025-06-25
NVDweakness (CWE)CWE-252read 2026-10-23
FIRST EPSSEPSS score3.4 %2026-10-22
OSVaffected packages—

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Published: 2022-08-24
Last Modified: 2026-10-14
NVD status: Modified

Frequently asked questions

What is CVE-2021-4189?

Is CVE-2021-4189 actively exploited?

Active exploitation of CVE-2021-4189 has not been confirmed. Its EPSS score was 3.4% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-4189?

CVE-2021-4189 has a CVSS v3 base score of 5.3 (MEDIUM severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N.

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