CVE-2021-43523 : Security Advisory and Response

In uClibc and uClibc-ng before 1.0.39, incorrect handling of special characters in domain names returned by DNS servers can lead to various security issues including domain hijacking and remote code execution.

Understanding CVE-2021-43523

What is CVE-2021-43523?

In uClibc and uClibc-ng before version 1.0.39, there is a vulnerability where special characters in domain names from DNS responses can cause incorrect output, potentially leading to domain hijacking or injection into applications.

The Impact of CVE-2021-43523

The vulnerability can result in serious consequences:

Domain hijacking
Remote code execution
Cross-Site Scripting (XSS)
Application crashes

Technical Details of CVE-2021-43523

Vulnerability Description

The flaw stems from inadequate handling of special characters in DNS responses, allowing for incorrect hostnames or application injection.

Affected Systems and Versions

All versions of uClibc and uClibc-ng prior to 1.0.39

Exploitation Mechanism

The vulnerability can be exploited by manipulating DNS responses with specially crafted domain names to trick the system into outputting incorrect hostnames or executing malicious code.

Mitigation and Prevention

Immediate Steps to Take

Update uClibc and uClibc-ng to version 1.0.39 or later
Monitor DNS responses for unusual or malicious domain names

Long-Term Security Practices

Implement input validation for DNS responses
Ensure proper error handling in applications

Patching and Updates

Apply patches provided by uClibc and uClibc-ng