ftpserver.py in pyftpdlib before 0.5.2 does not require the l permission for the MLST command, which allows remote authenticated users to bypass intended access restrictions and list the root directory via an FTP session.

References

• https://nvd.nist.gov/vuln/detail/CVE-2009-5012
• http://code.google.com/p/pyftpdlib/issues/detail?id=114
• GHSA-h4g7-8m7r-87r9
• https://github.com/pypa/advisory-database/tree/main/vulns/pyftpdlib/PYSEC-2010-9.yaml
• http://code.google.com/p/pyftpdlib/source/browse/trunk/HISTORY
• http://code.google.com/p/pyftpdlib/source/detail?r=596
• http://code.google.com/p/pyftpdlib/source/diff?spec=svn596&r=596&format=side&path=/trunk/pyftpdlib/ftpserver.py