CVE-2026-1519 is a denial of service vulnerability in ISC BIND 9 caused by unchecked input for loop conditions (CWE-606). When a BIND resolver validates DNSSEC and encounters a maliciously crafted zone, it may consume excessive CPU resources, leading to service disruption. The vulnerability affects multiple BIND 9 version ranges including 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, and their S1 variants. Authoritative-only servers are mostly unaffected unless they perform recursive queries. Red Hat has issued security advisories and errata with patches for affected Red Hat Enterprise Linux versions, indicating an official fix is available.

Successful exploitation of this vulnerability can cause a denial of service by consuming excessive CPU resources on BIND resolvers performing DNSSEC validation. This can degrade or disrupt DNS resolution services. There is no impact on confidentiality or integrity reported. Authoritative-only servers are generally not impacted unless they make recursive queries, which is uncommon. The CVSS v3.1 base score is 7.5, reflecting high severity due to network attack vector, low attack complexity, no privileges required, no user interaction, and impact limited to availability.

Official patches are available as per Red Hat security advisories and errata for affected Red Hat Enterprise Linux versions. Users should apply these updates promptly to remediate the vulnerability. Refer to Red Hat's advisory pages for detailed update instructions. No additional mitigation is indicated by the vendor advisory. Systems not running affected versions or not performing DNSSEC validation are not impacted.