CVE-2009-5010: Race Condition in pyftpdlib
Summary
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 (daemon outage) by establishing and then immediately closing a TCP connection, leading... Affects pyftpdlib versions < 0.5.1. Fixed in 0.5.1. 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 applications that require FTP server functionality. However, versions prior to 0.5.1 are vulnerable to a race condition that can lead to a denial of service (daemon outage) when a remote attacker establishes and immediately closes a TCP connection.
Vulnerability Detail
The vulnerability, identified as CVE-2009-5010, arises from a race condition in the FTPHandler class of pyftpdlib's ftpserver.py file. When a TCP connection is established and closed rapidly, the accept function may return an unexpected value of None. This unexpected behavior can cause a denial of service, resulting in a daemon outage. It is important to note that this vulnerability is distinct from CVE-2010-3494.
How To Fix
Minimum fixed version
0.5.1
This is the first release that contains the fix.
pip install --upgrade "pyftpdlib==0.5.1"Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
If updating pyftpdlib is not immediately feasible, a possible workaround is to implement proper synchronization mechanisms in the affected code. By ensuring that concurrent access to shared resources is properly synchronized, the race condition can be mitigated. Here is an example of how to use a lock to synchronize access to a shared resource:
import threading
lock = threading.Lock()
# Inside the critical section
lock.acquire()
try:
# Access the shared resource
finally:
lock.release()
Conclusion
In conclusion, pyftpdlib versions prior to 0.5.1 are vulnerable to a race condition that can result in a denial of service. It is crucial to update to the latest version of pyftpdlib (0.5.1 or later) to mitigate this vulnerability. If immediate updating is not possible, implementing proper synchronization mechanisms can serve as a temporary workaround. For further assistance or support in vulnerability remediation, please contact DevNack.com.
See every vulnerability recorded for pyftpdlib →
FAQ
pyftpdlib is a Python FTP server library that allows developers to create custom FTP servers with ease.
The vulnerability can lead to a denial of service (daemon outage) in applications that use pyftpdlib. An attacker can exploit the race condition by establishing and immediately closing a TCP connection.
Yes, updating pyftpdlib to version 0.5.1 or later fixes the vulnerability. It is recommended to update the library as soon as possible.
If updating pyftpdlib is not immediately feasible, developers can implement proper synchronization mechanisms in the affected code to mitigate the race condition. The provided code example demonstrates the use of a lock for synchronization.
No, this vulnerability (CVE-2009-5010) is distinct from CVE-2010-3494, although they both affect pyftpdlib.
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