CVE-2021-3448 : Security Advisory and Response

A flaw was found in dnsmasq in versions before 2.85, making DNS Cache Poisoning attacks easier.

Understanding CVE-2021-3448

This CVE affects dnsmasq, specifically version 2.85, and poses a threat to data integrity.

What is CVE-2021-3448?

CVE-2021-3448 is a vulnerability found in dnsmasq versions before 2.85 that allows an attacker on the network to conduct a DNS Cache Poisoning attack by guessing the random transmission ID.

The Impact of CVE-2021-3448

The vulnerability in dnsmasq can be exploited by an attacker on the network to forge a reply and have it accepted by dnsmasq, potentially leading to data integrity issues.

Technical Details of CVE-2021-3448

This section provides detailed technical information about the CVE.

Vulnerability Description

When dnsmasq is configured to use a specific server for a network interface, it uses a fixed port while forwarding queries. If an attacker can determine the outgoing port used by dnsmasq, they only need to guess the random transmission ID to execute a DNS Cache Poisoning attack.

Affected Systems and Versions

The vulnerability affects dnsmasq versions prior to 2.85.

Exploitation Mechanism

By finding the outgoing port used by dnsmasq and guessing the random transmission ID, an attacker can successfully conduct a DNS Cache Poisoning attack.

Mitigation and Prevention

To address CVE-2021-3448 and enhance security, follow these recommendations.

Immediate Steps to Take

Update dnsmasq to version 2.85 or later to mitigate the vulnerability.
Monitor network traffic for any suspicious activities.

Long-Term Security Practices

Regularly update software and patch known vulnerabilities.
Implement network segmentation to limit the attack surface.

Patching and Updates

Stay informed about security patches and updates released by dnsmasq to address vulnerabilities like CVE-2021-3448.