CVE-2021-29921 Explained : Impact and Mitigation

A vulnerability in the Python ipaddress library prior to version 3.9.5 allows attackers to bypass IP-based access controls by mishandling leading zero characters in IP address strings.

Understanding CVE-2021-29921

This CVE identifies a specific issue within the ipaddress library of Python that can be exploited in certain situations to circumvent IP address-based security measures.

What is CVE-2021-29921?

The vulnerability arises from the incorrect processing of leading zero characters in the octets of an IP address string. This mishandling could be exploited by threat actors to evade restrictions and permissions that rely on accurate IP address validation.

The Impact of CVE-2021-29921

By exploiting this vulnerability, attackers can potentially bypass IP address-centric security mechanisms, gaining unauthorized access to systems and services protected by IP filtering rules.

Technical Details of CVE-2021-29921

The following details shed light on the technical aspects of CVE-2021-29921:

Vulnerability Description

The flaw occurs in Python versions before 3.9.5 due to the mishandling of IP address strings with leading zero characters. This mishap can be leveraged to bypass IP address-based access controls.

Affected Systems and Versions

All Python versions prior to 3.9.5 are vulnerable to this ipaddress library issue. Systems relying on IP address validation for access control are particularly at risk.

Exploitation Mechanism

Attackers can exploit this vulnerability by crafting IP address strings with leading zeros in octets to deceive IP-based security mechanisms and gain unauthorized access.

Mitigation and Prevention

Implement the following measures to mitigate the risks associated with CVE-2021-29921:

Immediate Steps to Take

Update Python installations to version 3.9.5 or newer to remediate the ipaddress library vulnerability and prevent exploitation.

Long-Term Security Practices

Regularly monitor security advisories and apply patches promptly to safeguard against known vulnerabilities in third-party libraries and dependencies.

Patching and Updates

Stay informed about security updates and patches released by Python maintainers to address potential weaknesses in the ipaddress library and other components.