Cache-Poisoning Vulnerability in BIND 9 by ISC

CVE-2025-40776

What is CVE-2025-40776?

CVE-2025-40776 is a vulnerability identified within BIND 9, a widely used DNS (Domain Name System) software developed by the Internet Systems Consortium (ISC). BIND 9 serves as a caching resolver, responsible for translating human-readable domain names into IP addresses, thereby facilitating web traffic and various internet services. The vulnerability arises specifically in configurations where the caching resolver is set to send EDNS Client Subnet (ECS) options, potentially enabling attackers to perform cache-poisoning attacks. Such attacks can misdirect user traffic to malicious servers, jeopardizing data integrity and lead to unauthorized access. The versions affected include 9.11.3-S1 through 9.16.50-S1, 9.18.11-S1 through 9.18.37-S1, and 9.20.9-S1 through 9.20.10-S1.

Potential impact of CVE-2025-40776

1. Data Manipulation and Misdirection: Exploitation of this vulnerability can allow attackers to inject false DNS responses into the cache, resulting in end-users being directed to fraudulent sites. This poses a significant risk for data theft and phishing attempts.

2. Service Interruptions: By manipulating DNS caches, attackers can disrupt legitimate services, causing downtime or degradation of services used by businesses and individuals, impacting revenue and user trust.

3. Broader Network Compromise: Once an attacker gains control through cache poisoning, they can potentially navigate further into the network, leading to widespread vulnerabilities, data breaches, and the installation of malware. This chain effect puts entire organizational infrastructures at risk.

News Articles

Isc Kb

CVE-2025-40776

CVE-2025-40776: Birthday Attack against Resolvers supporting ECS

A resolver configured to send ECS options to authoritative servers can be compelled to make queries that slightly increase the odds of guessing the source port and other details necessary to bypass the original birthday cache poisoning attack mitigations. As a result of this weakness, a resolver wit...

2 days ago

References