# CVE-2019-18217: Denial of service in n/a

> Remote unauthenticated attackers can cause a denial of service in ProFTPD by sending overly long commands, triggering an infinite loop in the child process.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 21 Oct 2019
- **Updated:** 5 Aug 2024
- **Also known as:** DEBIAN-CVE-2019-18217, DLA-1974-1, DSA-4559-1, GHSA-5446-jrwr-x7c6, UBUNTU-CVE-2019-18217

## What is CVE-2019-18217?

CVE-2019-18217 is a high-severity denial of service vulnerability in n/a, published on 21 Oct 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

ProFTPD before 1.3.6b and 1.3.7rc before 1.3.7rc2 allows remote unauthenticated denial-of-service due to incorrect handling of overly long commands because main.c in a child process enters an infinite loop.

Weakness: CWE-835 (Loop with Unreachable Exit Condition)

## Which versions are affected by CVE-2019-18217?

It affects 1 product.


Products: Proftpd Proftpd.

## How do I fix CVE-2019-18217?

Upgrade to a fixed version.

## Is CVE-2019-18217 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2019-18217 exists.

Public exploit code:

- ProFTPD < 1.3.6b - Remote Unauthenticated DoS (nuclei)

## Other vulnerabilities in n/a

- [CVE-2010-4221](https://insights.sbomify.com/CVE-2010-4221/): Memory corruption in n/a (critical 10.0)
- [CVE-2010-20103](https://insights.sbomify.com/CVE-2010-20103/): ProFTPD 1.3.3c Backdoor Command Execution (critical 9.3)
- [CVE-2011-4130](https://insights.sbomify.com/CVE-2011-4130/): Use after free in n/a (critical 9.0)
- [CVE-2026-63090](https://insights.sbomify.com/CVE-2026-63090/): ProFTPD mod_sftp Heap Buffer Overflow via SFTP Packet Reassembly (high 8.7)
- [CVE-2026-35025](https://insights.sbomify.com/CVE-2026-35025/): ProFTPD ACL Bypass via /proc/self/root Path Prefix in RNFR (high 8.6)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2019-18217 and fix it if it is affected.

What it is: CVE-2019-18217 is a high-severity denial of service vulnerability in n/a, published on 21 Oct 2019. 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-2019-18217 exists.

Affected product: n/a. 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-2019-18217/ (Markdown: https://insights.sbomify.com/CVE-2019-18217/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2019-18217
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2019-18217
- OSV: https://osv.dev/vulnerability/CVE-2019-18217

---
From sbomify Insights: https://insights.sbomify.com/CVE-2019-18217/
Summaries are generated and may contain mistakes; the official description above is the record.