High [CVE-2026-13321] DNSSEC Validation Bypass via Out-of-Zone NSEC Next Field
This high-severity Red Hat Linux advisory covers CVE-2026-13321 affecting Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 7 Extended Lifecycle Support, Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support.
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Summary
The BIND resolver accepts validly-signed NSEC records where the "Next Domain Name" field points outside the signer's zone. This issue affects BIND 9 versions 9.11.0 through 9.18.50, 9.20.0 through 9.20.24, 9.21.0 through 9.21.23, 9.11.3-S1 through 9.18.50-S1, and 9.20.9-S1 through 9.20.24-S1.
An attacker controlling any DNSSEC-signed zone can craft NSEC records that span into victim zones, enabling cross-zone cache poisoning with authenticated denial-of-service responses (AD=1). Red Hat severity: Important — CVSS 8.6 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N).
Weakness: CWE-345.
Affected products named by the advisory: Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 7 Extended Lifecycle Support; Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support; Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On; and 12 more.
- 9.11.0
- 9.18.50
- 9.20.0
- 9.20.24
- 9.21.0
- 9.21.23
- 9.11.3
- 9.20.9
Official advisory · high-confidence parse· fetched 2 days ago·verify at source
- bind-32:9.18.33-15.el10_2.10
- bind-32:9.11.4-26.P2.el7_9.21
- bind9.16-32:9.16.23-0.22.el8_10.12
- bind-32:9.11.36-16.el8_10.14
- bind9.16-32:9.16.23-0.7.el8_6.11
- bind9.16-32:9.16.23-0.14.el8_8.9
- bind-32:9.16.23-40.el9_8.8
- bind9.18-32:9.18.29-14.el9_8.8
- bind-32:9.16.23-18.el9_4.12
- bind-32:9.16.23-31.el9_6.4
- openshift/ose-rhel-coreos-9:416.94.202609011112-0
- openshift/ose-rhel-coreos-9:417.94.202609191027-0
- openshift/ose-rhel-coreos-9:418.94.202609031320-0
- openshift/ose-rhel-coreos-9:418.94.202609171815-0
- openshift/ose-rhel-coreos-9:4.22.9.8.202608191915-0
- bind-main-9.20.26-0.1.hum1
- RHSA-2026:55437
- RHSA-2026:60383
- RHSA-2026:54509
- RHSA-2026:54654
- RHSA-2026:80501
- RHSA-2026:79160
- RHSA-2026:54510
- RHSA-2026:55442
- RHSA-2026:57189
- RHSA-2026:55441
- RHSA-2026:62549
- RHSA-2026:70586
- RHSA-2026:65851
- RHSA-2026:70615
- RHSA-2026:57362
- RHSA-2026:54071
Official advisory · high-confidence parse· fetched 2 days ago·verify at source
Mitigation checklist
- Disclaimer: The following mitigation notes are provided as a courtesy, pending the application of an official patch. This content was generated utilizing AI tools in conjunction with data from cmetaxonomy.org. Customers are advised to independently evaluate and test these temporary mitigations within their own infrastructure. ISC states no workarounds exist. Until patched, restrict the resolver to authorized client networks and deploy separate resolvers per trust zone. Memory hardening and auth controls don't apply — this is a DNS protocol logic error using validly-signed records.
Official advisory · high-confidence parse· fetched 2 days ago·verify at source
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