CVE-2026-2291 in dnsmasq
Summary
by MITRE • 05/11/2026
dnsmasqs extract_name() function can be abused to cause a heap buffer overflow, allowing an attacker to inject false DNS cache entries, which could result in DNS lookups to redirect to an attacker-controlled IP address, or to cause a DoS.
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Analysis
by VulDB Data Team • 07/21/2026
The vulnerability in dnsmasq's extract_name() function represents a critical heap buffer overflow condition that stems from inadequate input validation within the DNS resolution process. This flaw exists within the core packet parsing logic where the function fails to properly bounds-check data extracted from DNS query messages, allowing maliciously crafted DNS packets to overwrite adjacent heap memory regions. The vulnerability is classified under CWE-121 as a stack-based buffer overflow, though in this case it manifests as heap corruption due to the dynamic memory allocation patterns used by the software. Attackers can exploit this weakness by crafting specially formatted DNS queries containing oversized domain names or malformed compression pointers that cause the extract_name() function to write beyond allocated buffer boundaries, potentially corrupting heap metadata or adjacent memory structures.
The operational impact of this vulnerability extends beyond simple denial of service to enable sophisticated man-in-the-middle attacks through DNS cache poisoning. When successful, the heap overflow allows attackers to inject false DNS cache entries that can redirect legitimate network traffic to attacker-controlled IP addresses, effectively enabling DNS hijacking and traffic interception. This capability directly maps to ATT&CK technique T1071.004 for application layer protocol: dns, where adversaries manipulate DNS responses to redirect users to malicious infrastructure. The vulnerability affects dnsmasq installations across various network environments including home routers, enterprise networks, and cloud deployments where the software serves as a DNS forwarder or DHCP server, making it particularly dangerous due to its widespread deployment in critical network infrastructure components.
Mitigation strategies must address both immediate protection and long-term architectural improvements to prevent similar vulnerabilities from occurring in the future. Organizations should implement immediate patches from the dnsmasq maintainers that include proper bounds checking and input validation within the extract_name() function, ensuring that all domain name data is strictly validated against maximum length constraints before processing. Network administrators should also deploy DNS security measures such as DNSSEC validation and DNS query logging to detect anomalous DNS activity that might indicate exploitation attempts. The vulnerability demonstrates the importance of memory safety practices and aligns with industry standards for secure coding practices outlined in CWE-665, which emphasizes the need for proper initialization and bounds checking of all buffer operations. Additionally, implementing network segmentation and monitoring solutions can help detect and prevent exploitation attempts while maintaining operational continuity during patch deployment cycles.