CVE-2026-13321: DNSSEC Validation Bypass via Out-of-Zone NSEC Next Field

Published Jul 21, 2026
·
Updated

DNSSEC Validation Bypass via Out-of-Zone NSEC Next Field

Other sources

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.

— MITRE

The resolver accepts validly-signed NSEC records where the "Next Domain Name" field points outside the signer's zone. An attacker controlling ANY DNSSEC-signed zone can craft NSEC records spanning into victim zones, enabling cross-zone cache poisoning with AD=1 (Authenticated Data flag set)

— Red Hat

Affected Software

2 affected componentsFixes available
ISC BIND 9>=9.11.0<=9.18.50, >=9.20.0<=9.20.24, >=9.21.0<=9.21.23, >=9.11.3-S1<=9.18.50-S1, >=9.20.9-S1<=9.20.24-S1
Microsoft azl3 bind 9.20.23-1<9.20.26-1
9.20.26-1

Remediation

Recommended actions to resolve this vulnerability, in priority order.

  1. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 9.20.26-1
  2. Upgrade

    Upgrade ISC BIND 9 to a version that resolves this vulnerability.

    Fixed in 9.20.26
  3. Upgrade

    Upgrade ISC BIND 9 to a version that resolves this vulnerability.

    Fixed in 9.21.24
  4. Upgrade

    Upgrade ISC BIND 9 to a version that resolves this vulnerability.

    Fixed in 9.20.26-S1
  5. Compensating control

    Mitigate cross-zone cache poisoning by preventing acceptance/use of DNS responses with AD=1 when the response may contain out-of-zone NSEC 'Next Domain Name' values (e.g., apply resolver-side DNSSEC policy/validation constraints or strict DNSSEC validation posture consistent with vendor guidance) until the patched BIND 9 release is deployed.

Event History

Jul 21, 2026
Data Sourced
via Red Hat·07:47 PM
DescriptionSeverityAffected Software
Jul 22, 2026
CVE Published
via MITRE·02:16 PM
Data Sourced
via MITRE·02:16 PM
RemedyDescriptionSeverityWeakness
Data Sourced
via NVD·03:16 PM
DescriptionSeverityWeakness
Jul 25, 2026
Data Sourced
via Microsoft·08:04 AM
DescriptionSeverityWeakness
Data Sourced
via Microsoft·08:04 AM
Affected Software
Updated
via Microsoft·08:04 AM
DescriptionSeverity
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Frequently Asked Questions

1

What is the severity of CVE-2026-13321?

CVE-2026-13321 has a severity score of 8.6, categorized as high.

2

How do I fix CVE-2026-13321?

To fix CVE-2026-13321, upgrade to a patched version of ISC BIND 9 that is not affected by this vulnerability.

3

What versions of BIND are affected by CVE-2026-13321?

CVE-2026-13321 affects BIND 9 versions 9.11.0 through 9.18.50, 9.20.0 through 9.20.24, and 9.21.0 through 9.21.23.

4

What kind of attack is enabled by CVE-2026-13321?

CVE-2026-13321 allows for DNSSEC validation bypass via out-of-zone NSEC next field exploitation.

5

Who is affected by CVE-2026-13321?

Users and administrators of affected versions of ISC BIND 9 are at risk due to CVE-2026-13321.

Company

Resources

Contact

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