# CVE-2021-4189: Server-side request forgery in python

> A malicious FTP server can trick the Python FTP client into connecting to arbitrary internal hosts, enabling port scanning and potential data access.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 24 Aug 2022
- **Updated:** 14 Oct 2026
- **Also known as:** BIT-libpython-2021-4189, BIT-python-2021-4189, BIT-python-min-2021-4189, CLSA-2022-1649170553, CLSA-2022-1649348075, DEBIAN-CVE-2021-4189, GHSA-67xf-xphq-9mcc, UBUNTU-CVE-2021-4189, openSUSE-SU-2024:11835-1

## What is CVE-2021-4189?

CVE-2021-4189 is a medium-severity server-side request forgery vulnerability in Debian Debian Linux, published on 24 Aug 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-252 (Unchecked Return Value)

## Which versions are affected by CVE-2021-4189?

3 open source packages ship an affected version, including libpython, python and python-min. It affects 5 products.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `libpython` | Bitnami | From 3.6.0 | 3.6.14, 3.7.11, 3.8.9, 3.9.3, 3.10.1 |
| `python` | Bitnami | From 3.6.0 | 3.6.14, 3.7.11, 3.8.9, 3.9.3, 3.10.1 |
| `python-min` | Bitnami | From 3.6.0 | 3.6.14, 3.7.11, 3.8.9, 3.9.3, 3.10.1 |
| `python` | openSUSE:Tumbleweed | All versions | 2.7.18-15.1 |

Products: Debian Debian Linux, Netapp Ontap Select Deploy Administration Utility, Python Python, Redhat Enterprise Linux, Redhat Software Collections.

## How do I fix CVE-2021-4189?

Upgrade libpython to a fixed version for your release line: 3.6.14, 3.7.11, 3.8.9 or 3.9.3.

## Is CVE-2021-4189 being exploited?

There is no known exploitation of CVE-2021-4189 in the wild and no public exploit code.

## Other vulnerabilities in Debian Debian Linux

- [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild)
- [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild)
- [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild)
- [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild)
- [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-4189 and fix it if it is affected.

What it is: CVE-2021-4189 is a medium-severity server-side request forgery vulnerability in Debian Debian Linux, published on 24 Aug 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-4189 in the wild and no public exploit code.

Affected packages and fixed versions:
- libpython (Bitnami): affected from 3.6.0; fixed in 3.6.14, 3.7.11, 3.8.9, 3.9.3, 3.10.1
- python (Bitnami): affected from 3.6.0; fixed in 3.6.14, 3.7.11, 3.8.9, 3.9.3, 3.10.1
- python-min (Bitnami): affected from 3.6.0; fixed in 3.6.14, 3.7.11, 3.8.9, 3.9.3, 3.10.1

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2021-4189/ (Markdown: https://insights.sbomify.com/CVE-2021-4189/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-4189
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-4189
- OSV: https://osv.dev/vulnerability/CVE-2021-4189

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-4189/
Summaries are generated and may contain mistakes; the official description above is the record.