CVE-2026-0398 in Recursor
Summary
by MITRE • 02/09/2026
Crafted zones can lead to increased resource usage and crafted CNAME chains can lead to cache poisoning in Recursor.
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Analysis
by VulDB Data Team • 02/11/2026
The vulnerability identified as CVE-2026-0398 represents a significant security flaw in DNS recursor implementations that can be exploited through carefully crafted zone data and CNAME chain manipulation. This vulnerability specifically targets the recursive DNS resolution process where maliciously constructed DNS zones and CNAME records can be used to consume excessive system resources while simultaneously creating opportunities for cache poisoning attacks. The flaw exploits the way DNS resolvers handle zone data processing and CNAME chain traversal, potentially allowing attackers to exhaust memory and CPU resources through resource-intensive operations while simultaneously corrupting DNS cache entries.
The technical implementation of this vulnerability stems from insufficient input validation and resource management within the DNS recursor's zone processing logic. When processing crafted zone data, the resolver may enter into inefficient processing loops or allocate excessive memory structures that grow exponentially with the complexity of the malicious zone data. Additionally, the vulnerability extends to CNAME chain handling where attackers can construct chains of CNAME records that cause the resolver to traverse deep recursive paths, leading to both resource exhaustion and cache poisoning opportunities. This behavior aligns with CWE-400 which addresses improper resource management and CWE-20 which covers input validation flaws that can lead to resource exhaustion attacks.
The operational impact of CVE-2026-0398 can be severe for organizations relying on DNS infrastructure, as the vulnerability can be exploited to perform denial of service attacks against DNS resolvers while simultaneously compromising DNS cache integrity. Attackers can consume significant system resources through resource-heavy zone processing operations, potentially leading to service disruption and making legitimate DNS queries fail. The cache poisoning aspect of this vulnerability allows attackers to inject malicious DNS responses into the resolver's cache, redirecting traffic to malicious destinations and enabling various attack vectors including man-in-the-middle attacks, phishing operations, and redirection of network traffic to attacker-controlled systems. This vulnerability directly maps to ATT&CK technique T1071.004 which covers DNS tunneling and cache poisoning, and T1496 which addresses resource exhaustion attacks targeting network infrastructure.
Mitigation strategies for CVE-2026-0398 should focus on implementing robust input validation mechanisms and resource limits within DNS resolvers to prevent excessive processing of malformed zone data. Organizations should configure their DNS resolvers with appropriate limits on zone size, CNAME chain depth, and memory allocation for DNS processing operations. Implementing rate limiting and connection throttling mechanisms can help prevent resource exhaustion attacks while deploying monitoring systems to detect unusual DNS processing patterns that may indicate exploitation attempts. Network administrators should also consider implementing DNS security extensions such as DNSSEC to provide additional protection against cache poisoning attacks, and regularly update their DNS resolver software to incorporate patches that address the specific resource management flaws identified in this vulnerability. The implementation of these mitigations should align with industry best practices for DNS security and follow guidelines established by organizations such as the IETF and NIST for secure DNS infrastructure deployment and management.