# CVE-2021-4432: PCMan FTP Server USER Command denial of service

> Remote attackers can cause a denial of service in PCMan FTP Server by exploiting the USER command handler.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 16 Jan 2024
- **Updated:** 17 Jun 2025
- **Also known as:** GHSA-v462-3xw3-jqx3

## What is CVE-2021-4432?

CVE-2021-4432 is a medium-severity denial of service vulnerability in Pcman Ftp Server, published on 16 Jan 2024. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A vulnerability was found in PCMan FTP Server 2.0.7. It has been classified as problematic. This affects an unknown part of the component USER Command Handler. The manipulation leads to denial of service. It is possible to initiate the attack remotely. The exploit has been disclosed to the public and may be used. The associated identifier of this vulnerability is VDB-250719.

Weakness: CWE-404 (Improper Resource Shutdown or Release)

## Which versions are affected by CVE-2021-4432?

It affects 1 product.


Products: Pcman Ftp Server.

## How do I fix CVE-2021-4432?

No fix has been published for CVE-2021-4432 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-4432 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-4432 exists.

## Other vulnerabilities in Pcman Ftp Server

- [CVE-2013-4730](https://insights.sbomify.com/CVE-2013-4730/): Memory corruption in n/a (critical 10.0)
- [CVE-2018-18861](https://insights.sbomify.com/CVE-2018-18861/): Memory corruption in n/a (critical 9.8)
- [CVE-2015-7601](https://insights.sbomify.com/CVE-2015-7601/): Path traversal in n/a (high 7.8)
- [CVE-2025-5634](https://insights.sbomify.com/CVE-2025-5634/): PCMan FTP Server NOOP Command buffer overflow (medium 6.9)
- [CVE-2025-5635](https://insights.sbomify.com/CVE-2025-5635/): PCMan FTP Server PLS Command buffer overflow (medium 6.9)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-4432 and fix it if it is affected.

What it is: CVE-2021-4432 is a medium-severity denial of service vulnerability in Pcman Ftp Server, published on 16 Jan 2024. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-4432 exists.

Affected product: Pcman Ftp Server. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2021-4432/ (Markdown: https://insights.sbomify.com/CVE-2021-4432/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-4432
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-4432
- OSV: https://osv.dev/vulnerability/CVE-2021-4432

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-4432/
Summaries are generated and may contain mistakes; the official description above is the record.