CVE-2026-1519 in BIND
Summary
by MITRE • 03/25/2026
If a BIND resolver is performing DNSSEC validation and encounters a maliciously crafted zone, the resolver may consume excessive CPU. Authoritative-only servers are generally unaffected, although there are circumstances where authoritative servers may make recursive queries (see: https://kb.isc.org/docs/why-does-my-authoritative-server-make-recursive-queries). This issue affects BIND 9 versions 9.11.0 through 9.16.50, 9.18.0 through 9.18.46, 9.20.0 through 9.20.20, 9.21.0 through 9.21.19, 9.11.3-S1 through 9.16.50-S1, 9.18.11-S1 through 9.18.46-S1, and 9.20.9-S1 through 9.20.20-S1.
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Analysis
by VulDB Data Team • 05/26/2026
The vulnerability described in CVE-2026-1519 represents a significant performance degradation issue within the Berkeley Internet Name Domain (BIND) resolver implementation. This flaw specifically manifests when DNSSEC validation is actively enabled on a resolver system and encounters malformed or maliciously crafted DNS zone data. The security implications extend beyond simple resource exhaustion as the vulnerability can potentially be exploited to disrupt legitimate DNS services through sustained CPU consumption attacks. The issue affects a broad range of BIND 9 versions across multiple release streams, indicating a widespread exposure that requires immediate attention from network administrators and security teams responsible for DNS infrastructure.
The technical root cause of this vulnerability lies in the DNSSEC validation processing logic within BIND's resolver component. When processing DNS zone data that contains specific malformed structures or crafted anomalies, the resolver enters into an inefficient processing loop that consumes disproportionate CPU cycles. This behavior occurs during the validation phase of DNSSEC records where the resolver attempts to verify cryptographic signatures and chain of trust. The flaw does not affect authoritative servers under normal operation, but as noted in the advisory, there are specific scenarios where authoritative servers may initiate recursive queries, thereby exposing them to this vulnerability. This cross-over behavior demonstrates the interconnected nature of DNS infrastructure where resolver functionality can inadvertently affect authoritative server operations.
The operational impact of CVE-2026-1519 extends beyond simple denial of service conditions to potentially compromise the overall stability and performance of DNS services. Attackers could exploit this vulnerability through sustained resource exhaustion attacks that gradually consume CPU resources until the system becomes unresponsive or fails to handle legitimate DNS queries effectively. The vulnerability affects the resolver component specifically, meaning that systems configured to perform DNSSEC validation on incoming queries would be at risk, while those configured to perform only authoritative service or non-DNSSEC validation would remain unaffected. This selective exposure creates a complex operational environment where network security teams must carefully evaluate their DNS configurations and determine appropriate mitigation strategies.
Mitigation strategies for this vulnerability should prioritize immediate patching of affected BIND versions, as the issue affects multiple release streams including 9.11.0 through 9.16.50, 9.18.0 through 9.18.46, 9.20.0 through 9.20.20, and 9.21.0 through 9.21.19. Organizations should also consider implementing temporary workarounds such as disabling DNSSEC validation on resolvers until patches can be deployed, though this reduces security protection. Network monitoring should be enhanced to detect unusual CPU consumption patterns that might indicate exploitation attempts. The vulnerability aligns with ATT&CK technique T1496 for resource exhaustion and CWE-400 for unchecked resource consumption, highlighting the need for proper input validation and resource management in DNS processing components. Additionally, implementing rate limiting and query monitoring can provide early detection of potential exploitation attempts while maintaining operational functionality.