CVE-2026-13321
HIGHCVE-2026-13321 is a high-severity (CVSS 8.6) CWE-346 vulnerability. No vendor fix is recorded yet; mitigation options are listed below.
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,…
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-13321.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-13321 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 393,867 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Description
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.
Detection & mitigation playbook
VulnerabilityDetect
Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).
Remediation status
No fixed release is recorded for CVE-2026-13321 yet. Track the upstream advisory, and apply the exposure-reduction steps below in the meantime.
Mitigate without a patch
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
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).
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.Source: Red Hat security advisory for CVE-2026-13321 (CC BY 4.0)
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Enterprise Linux 10 | bind-32:9.18.33-15.el10_2.10 | RHSA-2026:55437 |
| Red Hat Enterprise Linux 7 Extended Lifecycle Support | bind-32:9.11.4-26.P2.el7_9.21 | RHSA-2026:60383 |
| Red Hat Enterprise Linux 8 | bind9.16-32:9.16.23-0.22.el8_10.12 | RHSA-2026:54509 |
| Red Hat Enterprise Linux 8 | bind-32:9.11.36-16.el8_10.14 | RHSA-2026:54654 |
| Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support | bind9.16-32:9.16.23-0.7.el8_6.11 | RHSA-2026:80501 |
| Red Hat Enterprise Linux 8.8 Telecommunications Update Service | bind9.16-32:9.16.23-0.14.el8_8.9 | RHSA-2026:79160 |
| Red Hat Enterprise Linux 9 | bind-32:9.16.23-40.el9_8.8 | RHSA-2026:54510 |
| Red Hat Enterprise Linux 9 | bind9.18-32:9.18.29-14.el9_8.8 | RHSA-2026:55442 |
Frequently Asked Questions
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