CVE-2007-6737: pyftpdlib FTPServer.py Invalid Username Brute-Force Vulnerability
Summary
CVE-2007-6737: FTPServer.py in pyftpdlib before 0.2.0 does not increment the attempted_logins count for a USER command that specifies an invalid username, which makes it easier for remote attackers to obtain access via a brute-force at... Affects pyftpdlib versions < 0.2.0. Fixed in 0.2.0. How to fix ↓
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Background
pyftpdlib is a Python FTP server library that provides a high-level interface for implementing FTP servers. It allows developers to create custom FTP servers with ease. The library is widely used in various Python projects and is available on the Python Package Index (PyPI).
Vulnerability Detail
The vulnerability (CVE-2007-6737) exists in pyftpdlib versions prior to 0.2.0. When a USER command specifies an invalid username, the attempted_logins count is not incremented. This oversight makes it easier for remote attackers to launch brute-force attacks and gain unauthorized access to the FTP server. By repeatedly attempting different usernames, an attacker can exploit this vulnerability to guess valid usernames and potentially compromise the server.
How To Fix
Latest published version: 2.2.0 as of 23 Oct 2026
pip install --upgrade "pyftpdlib==2.2.0"Upgrading to it may include breaking changes; the version below is the minimum fixed release for this vulnerability.
If you need the minimum change
0.2.0
This is the first release that contains the fix.
pip install --upgrade "pyftpdlib==0.2.0"Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
There is no known workaround for this vulnerability. It is crucial to update to the fixed version of pyftpdlib as soon as possible.
Conclusion
The pyftpdlib FTPServer.py Invalid Username Brute-Force Vulnerability (CVE-2007-6737) allows remote attackers to gain unauthorized access to FTP servers by exploiting the lack of incrementation in the attempted_logins count for invalid usernames. To mitigate this vulnerability, it is crucial to update to pyftpdlib version 0.2.0 or later. For further assistance with vulnerability remediation, please contact DevNack.com.
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FAQ
pyftpdlib is a Python FTP server library that allows developers to create custom FTP servers.
Versions of pyftpdlib prior to 0.2.0 are affected.
An attacker can exploit this vulnerability by launching a brute-force attack, repeatedly attempting different usernames until a valid one is found.
If successfully exploited, this vulnerability can allow remote attackers to gain unauthorized access to the FTP server and potentially compromise sensitive data.
No, there is no known workaround. It is essential to update to the fixed version of pyftpdlib.
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