CVE-2021-3733 : Security Advisory and Response
Get insights into CVE-2021-3733, a flaw in Python urllib AbstractBasicAuthHandler enabling Regular Expression Denial of Service attacks. Learn impact, affected versions, and mitigation steps.
A flaw in urllib's AbstractBasicAuthHandler class can lead to a Regular Expression Denial of Service (ReDOS) attack, affecting Python versions. Learn about the impact, technical details, and mitigation steps.
Understanding CVE-2021-3733
This CVE involves a vulnerability in urllib's AbstractBasicAuthHandler class that could be exploited by an attacker to trigger a ReDOS attack.
What is CVE-2021-3733?
The flaw allows an attacker controlling a malicious HTTP server to exploit an HTTP client, potentially causing a denial of service through a specially crafted payload during an authentication request.
The Impact of CVE-2021-3733
The primary risk associated with this vulnerability is a threat to application availability due to an attacker causing a ReDOS attack.
Technical Details of CVE-2021-3733
This section outlines the vulnerability description, affected systems, and the exploitation mechanism.
Vulnerability Description
The flaw in urllib's AbstractBasicAuthHandler could be triggered by a specially crafted payload, leading to a ReDOS attack during an authentication request.
Affected Systems and Versions
Python versions affected include python v3.6.14, python v3.7.11, python v3.8.10, and python v3.9.5. The issue has been fixed in these versions.
Exploitation Mechanism
An attacker controlling a malicious HTTP server can exploit the vulnerability during an authentication request to trigger a ReDOS attack.
Mitigation and Prevention
Discover immediate steps to take and best security practices to safeguard against CVE-2021-3733.
Immediate Steps to Take
Users are advised to update their Python versions to the fixed releases, including python v3.6.14, v3.7.11, v3.8.10, and v3.9.5, to prevent exploitation.
Long-Term Security Practices
Implementing secure coding practices, monitoring network traffic, and applying regular security updates are essential to mitigate the risk of ReDOS attacks.
Patching and Updates
Regularly check for security updates from Python and apply patches promptly to maintain a secure environment.