What’s Vulnerable › Vulnerabilities

CVE-2026-1519: Excessive NSEC3 iterations cause high CPU load during insecure delegation validation

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.7% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-03-25 · updated 2026-09-17
• Weakness: CWE-606

Description

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.

Affected products

• ISC BIND: from 9.11.0 through 9.16.50; from 9.18.0 before 9.18.47; from 9.20.0 before 9.20.21; from 9.21.0 before 9.21.20 — fixed in 9.18.47, 9.20.21, 9.21.20

How to fix

Upgrade to a fixed version: ISC BIND 9.18.47, 9.20.21, 9.21.20. Check the vendor advisory for mitigations.

References

• https://downloads.isc.org/isc/bind9/9.18.47
• https://downloads.isc.org/isc/bind9/9.20.21
• https://downloads.isc.org/isc/bind9/9.21.20
• https://kb.isc.org/docs/cve-2026-1519
• https://lists.debian.org/debian-lts-announce/2026/04/msg00008.html
• https://access.redhat.com/errata/RHSA-2026:11371
• https://access.redhat.com/errata/RHSA-2026:11372
• https://access.redhat.com/errata/RHSA-2026:15890
• https://access.redhat.com/errata/RHSA-2026:16060
• https://access.redhat.com/errata/RHSA-2026:16064
• https://access.redhat.com/errata/RHSA-2026:24500
• https://access.redhat.com/errata/RHSA-2026:24851

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