CVE-2021-4189
What it is
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.
At a glance
- Exploitability
- Can be exploited over the network without logging in. Limited direct impact.
- Exploit odds
- 3.4% chance of exploitation in the next 30 days (EPSS).
- Fix
- A patch, advisory or fixed version is referenced. Upgrade or apply it.
Timeline
- PublishedDisclosed publicly on CVE.org and NVD
- Last updatedMost recent change to the record
Why it ranks here
- Exploited in the wild: no, CISA does not list it.
- Exploit odds: 3.4% in the next 30 days (EPSS).
- Severity: 5.3 MEDIUM (CVSS).
- Fix: a patch or advisory is linked.
Details
- Published
- Last modified
- Exploit probability
- 3.4% · EPSS, next 30 days
- Weakness
- CWE-252
- Record status
- Modified
Affected
- Python < 3.6.14
- Python < 3.7.11
- Python < 3.8.9
- Python < 3.9.3
- Python 3.10.0
- Debian Linux 10.0
- Debian Linux 11.0
- Redhat Software Collections
Attack profile CVSS 3.1 · 5.3
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- Low
- Integrity
- None
- Availability
- None
Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Is it in your code?
Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.
Read https://cve-list.com/agent/cve/CVE-2021-4189.md and follow it. Check whether this project is affected by CVE-2021-4189. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.
Fix and advisories
- https://bugs.python.org/issue43285
- https://bugzilla.redhat.com/show_bug.cgi?id=2036020
- https://github.com/python/cpython/commit/0ab152c6b5d95caa2dc1a30fa96e10258b5f188e
- https://python-security.readthedocs.io/vuln/ftplib-pasv.html
- https://bugs.python.org/issue43285
- https://bugzilla.redhat.com/show_bug.cgi?id=2036020
- https://github.com/python/cpython/commit/0ab152c6b5d95caa2dc1a30fa96e10258b5f188e
- https://python-security.readthedocs.io/vuln/ftplib-pasv.html
References
- https://access.redhat.com/security/cve/CVE-2021-4189
- https://bugs.python.org/issue43285
- https://bugzilla.redhat.com/show_bug.cgi?id=2036020
- https://github.com/python/cpython/commit/0ab152c6b5d95caa2dc1a30fa96e10258b5f188e
- https://lists.debian.org/debian-lts-announce/2023/05/msg00024.html
- https://lists.debian.org/debian-lts-announce/2023/06/msg00039.html
- https://python-security.readthedocs.io/vuln/ftplib-pasv.html
- https://security-tracker.debian.org/tracker/CVE-2021-4189
- https://security.netapp.com/advisory/ntap-20221104-0004/
- https://access.redhat.com/security/cve/CVE-2021-4189
- https://bugs.python.org/issue43285
- https://bugzilla.redhat.com/show_bug.cgi?id=2036020
- https://github.com/python/cpython/commit/0ab152c6b5d95caa2dc1a30fa96e10258b5f188e
- https://lists.debian.org/debian-lts-announce/2023/05/msg00024.html
- https://lists.debian.org/debian-lts-announce/2023/06/msg00039.html
- https://lists.debian.org/debian-lts-announce/2024/12/msg00000.html
- https://python-security.readthedocs.io/vuln/ftplib-pasv.html
- https://security-tracker.debian.org/tracker/CVE-2021-4189
- https://security.netapp.com/advisory/ntap-20221104-0004/
- https://cert-portal.siemens.com/productcert/html/ssa-398330.html