CVE-2020-25683 : Security Advisory and Response

A heap-based buffer overflow vulnerability was discovered in dnsmasq before version 2.83, potentially leading to a denial of service attack.

Understanding CVE-2020-25683

This CVE involves a critical flaw in dnsmasq that could be exploited by a remote attacker to crash the service, impacting system availability.

What is CVE-2020-25683?

The vulnerability in dnsmasq allows an attacker to trigger a heap-based buffer overflow by sending crafted DNS replies, leading to a denial of service condition.

The Impact of CVE-2020-25683

The primary risk posed by this vulnerability is to system availability, as an attacker could exploit it to crash dnsmasq, causing a denial of service.

Technical Details of CVE-2020-25683

This section provides more in-depth technical information about the vulnerability.

Vulnerability Description

The flaw in dnsmasq before version 2.83 is a heap-based buffer overflow triggered when DNSSEC is enabled, allowing an attacker to crash the service by causing an overflow in heap-allocated memory.

Affected Systems and Versions

Product: dnsmasq
Vendor: n/a
Vulnerable Version: dnsmasq 2.83

Exploitation Mechanism

The vulnerability arises from the lack of length checks in rfc1035.c:extract_name(), enabling an attacker to execute memcpy() with a negative size in get_rdata() and crash dnsmasq.

Mitigation and Prevention

Protecting systems from CVE-2020-25683 requires immediate actions and long-term security practices.

Immediate Steps to Take

Update dnsmasq to version 2.83 or later to mitigate the vulnerability.
Disable DNSSEC if not required to reduce the attack surface.

Long-Term Security Practices

Regularly monitor for security advisories and updates related to dnsmasq.
Implement network segmentation to limit the impact of potential attacks.

Patching and Updates

Apply patches provided by the vendor promptly to address security vulnerabilities and protect the system.