Is CVE-2021-4189 in the CISA KEV catalog?

No. CVE-2021-4189 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2021-4189?

CVE-2021-4189 has a CVSS v3 base score of 5.3 (MEDIUM).

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

CVE-2021-4189 has an EPSS score of 2.60% (84th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2021-4189?

Upgrade pypy3 on debian 11 to 7.3.5+dfsg-2 or later. Fixes are available for 29 affected products.

CVE & CISA-KEV Catalog

CVE-2021-4189

MEDIUMEPSS 84th pctl

5.3

CVSS v3

NVD

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.

CWE-252

How to fix

Remediation Available

pypy3Debian

Fixed in:7.3.5+dfsg-2CVE-2021-4189

libpython3.10Ubuntu

Fixed in:3.10.12-1~22.04.16USN-8509-1

libpython3.12t64Ubuntu

Fixed in:3.12.3-1ubuntu0.15USN-8509-1

python2.7Ubuntu

Fixed in:2.7.6-8ubuntu0.6+esm12USN-5342-2

Fixed in:2.7.12-1ubuntu0~16.04.18+esm1USN-5342-1

Fixed in:2.7.17-1~18.04ubuntu1.7USN-5342-1

Fixed in:2.7.18-1~20.04.3+esm1USN-5342-2

Fixed in:2.7.18-13ubuntu1.1+esm2USN-5342-2

python2.7-minimalUbuntu

Fixed in:2.7.6-8ubuntu0.6+esm12USN-5342-2

Fixed in:2.7.12-1ubuntu0~16.04.18+esm1USN-5342-1

Fixed in:2.7.17-1~18.04ubuntu1.7USN-5342-1

Fixed in:2.7.18-1~20.04.3+esm1USN-5342-2

Fixed in:2.7.18-13ubuntu1.1+esm2USN-5342-2

python3.10Ubuntu

Fixed in:3.10.12-1~22.04.16USN-8509-1

Fixed in:3.10.12-1~22.04.4USN-6891-1

python3.10-minimalUbuntu

Fixed in:3.10.12-1~22.04.4USN-6891-1

python3.11Ubuntu

Fixed in:3.11.0~rc1-1~22.04.1~esm1USN-6891-1

Fixed in:3.11.6-3ubuntu0.1USN-6891-1

python3.11-minimalUbuntu

Fixed in:3.11.0~rc1-1~22.04.1~esm1USN-6891-1

Fixed in:3.11.6-3ubuntu0.1USN-6891-1

python3.12Ubuntu

Fixed in:3.12.0-1ubuntu0.1USN-6891-1

Fixed in:3.12.3-1ubuntu0.15USN-8509-1

python3.12-minimalUbuntu

Fixed in:3.12.0-1ubuntu0.1USN-6891-1

python3.4Ubuntu

Fixed in:3.4.3-1ubuntu1~14.04.7+esm12USN-5342-1

python3.4-minimalUbuntu

Fixed in:3.4.3-1ubuntu1~14.04.7+esm12USN-5342-1

python3.5Ubuntu

Fixed in:3.5.2-2ubuntu0~16.04.4~14.04.1+esm1USN-6891-1

Fixed in:3.5.2-2ubuntu0~16.04.13+esm13USN-6891-1

Fixed in:3.5.2-2ubuntu0~16.04.13+esm2USN-5342-1

python3.5-minimalUbuntu

Fixed in:3.5.2-2ubuntu0~16.04.4~14.04.1+esm1USN-6891-1

Fixed in:3.5.2-2ubuntu0~16.04.13+esm13USN-6891-1

Fixed in:3.5.2-2ubuntu0~16.04.13+esm2USN-5342-1

python3.6Ubuntu

Fixed in:3.6.9-1~18.04ubuntu1.13+esm2USN-6891-1

Fixed in:3.6.9-1~18.04ubuntu1.7USN-5342-1

python3.6-minimalUbuntu

Fixed in:3.6.9-1~18.04ubuntu1.7USN-5342-1

Fixed in:3.6.9-1~18.04ubuntu1.13+esm2USN-6891-1

python3.7Ubuntu

Fixed in:3.7.5-2ubuntu1~18.04.2+esm3USN-6891-1

python3.7-minimalUbuntu

Fixed in:3.7.5-2ubuntu1~18.04.2+esm3USN-6891-1

python3.8Ubuntu

Fixed in:3.8.0-3ubuntu1~18.04.2+esm2USN-6891-1

Fixed in:3.8.10-0ubuntu1~20.04.4USN-5342-1

Fixed in:3.8.10-0ubuntu1~20.04.10USN-6891-1

python3.8-minimalUbuntu

Fixed in:3.8.0-3ubuntu1~18.04.2+esm2USN-6891-1

Fixed in:3.8.10-0ubuntu1~20.04.10USN-6891-1

Fixed in:3.8.10-0ubuntu1~20.04.4USN-5342-1

python3.9Ubuntu

Fixed in:3.9.5-3ubuntu0~20.04.1+esm2USN-6891-1

python3.9-minimalUbuntu

Fixed in:3.9.5-3ubuntu0~20.04.1+esm2USN-6891-1

Python 2Windows application

Affected:3.7.0 3.7.11Fixed in:3.7.11Python Software Foundation

Affected:3.9.0 3.9.3Fixed in:3.9.3Python Software Foundation

Affected:3.6.0 3.6.14Fixed in:3.6.14Python Software Foundation

Affected:3.8.0 3.8.9Fixed in:3.8.9Python Software Foundation

Python 3.10Windows application

Affected:3.8.0 3.8.9Fixed in:3.8.9Python Software Foundation

Affected:3.6.0 3.6.14Fixed in:3.6.14Python Software Foundation

Affected:3.9.0 3.9.3Fixed in:3.9.3Python Software Foundation

Affected:3.7.0 3.7.11Fixed in:3.7.11Python Software Foundation

Python 3.11Windows application

Affected:3.8.0 3.8.9Fixed in:3.8.9Python Software Foundation

Affected:3.9.0 3.9.3Fixed in:3.9.3Python Software Foundation

Affected:3.6.0 3.6.14Fixed in:3.6.14Python Software Foundation

Affected:3.7.0 3.7.11Fixed in:3.7.11Python Software Foundation

Python 3.12Windows application

Affected:3.6.0 3.6.14Fixed in:3.6.14Python Software Foundation

Affected:3.9.0 3.9.3Fixed in:3.9.3Python Software Foundation

Affected:3.8.0 3.8.9Fixed in:3.8.9Python Software Foundation

Affected:3.7.0 3.7.11Fixed in:3.7.11Python Software Foundation

Python 3.8Windows application

Affected:3.7.0 3.7.11Fixed in:3.7.11Python Software Foundation

Affected:3.9.0 3.9.3Fixed in:3.9.3Python Software Foundation

Affected:3.8.0 3.8.9Fixed in:3.8.9Python Software Foundation

Affected:3.6.0 3.6.14Fixed in:3.6.14Python Software Foundation

Python 3.9Windows application

Affected:3.7.0 3.7.11Fixed in:3.7.11Python Software Foundation

Affected:3.9.0 3.9.3Fixed in:3.9.3Python Software Foundation

Affected:3.8.0 3.8.9Fixed in:3.8.9Python Software Foundation

Affected:3.6.0 3.6.14Fixed in:3.6.14Python Software Foundation

TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

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

Exploit Intelligence

2.60%probability of exploitation in 30 days

84thpercentile

Elevated risk: more likely to be exploited than 84% of all known CVEs.

References

Patch4

Third-Party Advisory3

Other references3

Related Vulnerabilities

Other CWE-252 vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2005-4360	High	7.8	87%	-	-
CVE-2007-3798	Critical	9.8	70%	-	Fix
CVE-2010-0211	Critical	9.8	29%	-	Fix
CVE-2022-23626	High	8.5	9.9%	-	Fix
CVE-2019-10902	High	7.5	4.7%	-	-
CVE-2018-20216	High	7.5	3.9%	-	Fix

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2025-12-17.