CVE-2026-66374 in Knot Resolver
Summary
by MITRE • 07/25/2026
Knot Resolver before 6.4.1 allows remote code execution via a heap-based buffer overflow in the DoQ (DNS-over-QUIC) receive path.
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Analysis
by VulDB Data Team • 07/26/2026
The vulnerability in Knot Resolver versions prior to 6.4.1 represents a critical heap-based buffer overflow within the DNS-over-QUIC implementation that enables remote code execution. This flaw exists specifically in the DoQ receive path processing mechanism where incoming QUIC packets are handled and parsed. The buffer overflow occurs when the resolver processes malformed or specially crafted DNS queries transmitted over QUIC protocol, creating an opportunity for attackers to execute arbitrary code on the affected system with the privileges of the running process.
The technical implementation of this vulnerability stems from insufficient input validation and memory management within the QUIC packet handling components of Knot Resolver. When processing incoming DoQ frames, the software fails to properly bounds-check data received from network connections, allowing an attacker to overflow heap-allocated buffers and potentially overwrite adjacent memory regions. This type of vulnerability falls under CWE-121 Heap-based Buffer Overflow, which is classified as a high-risk issue due to its potential for arbitrary code execution. The attack vector requires network access to the resolver service and can be executed remotely without authentication, making it particularly dangerous in production environments.
The operational impact of this vulnerability extends beyond simple privilege escalation to potentially compromise entire DNS infrastructure services. An attacker could leverage this flaw to gain full control over a Knot Resolver instance, enabling them to manipulate DNS responses, perform cache poisoning attacks, or redirect traffic to malicious endpoints. Given that DNS resolvers often serve as critical infrastructure components in network environments, the potential for widespread disruption is significant. The vulnerability affects systems running Knot Resolver versions 6.4.0 and earlier, including those deployed in enterprise networks, cloud environments, and internet service provider infrastructures where DNS resolution services are integral to operations.
Mitigation strategies for this vulnerability primarily involve upgrading to Knot Resolver version 6.4.1 or later, which includes patched buffer handling routines and improved input validation for QUIC packet processing. Organizations should also implement network segmentation controls to limit access to DNS resolver services, employ intrusion detection systems that can identify anomalous DoQ traffic patterns, and consider deploying additional monitoring tools to detect potential exploitation attempts. From a defensive perspective, this vulnerability aligns with ATT&CK technique T1059.007 for Command and Scripting Interpreter: PowerShell, as attackers may attempt to leverage the compromised resolver for further network infiltration. System administrators should also review their existing security policies and ensure that DNS infrastructure is properly hardened against remote access attempts while maintaining proper audit logging capabilities to detect potential exploitation activities.