CVE-2026-13321: DNSSEC Validation Bypass via Out-of-Zone NSEC Next Field
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
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 9.20.26-1 - Upgrade
Upgrade
debian/bind9to a version that resolves this vulnerability.Fixed in 1:9.16.50-1~deb11u6Fixed in 1:9.18.49-1~deb12u2Fixed in 1:9.20.26-1~deb13u1Fixed in 1:9.20.26-1Fixed in 1:9.20.27-1 - Upgrade
Upgrade
BIND 9to a version that resolves this vulnerability.Fixed in 9.20.26 - Upgrade
Upgrade
BIND 9to a version that resolves this vulnerability.Fixed in 9.21.24 - Upgrade
Upgrade
BIND 9to a version that resolves this vulnerability.Fixed in 9.20.26-S1 - Compensating control
Until the patched BIND 9 release is deployed, mitigate cross-zone cache poisoning risk by restricting DNS resolver traffic/queries to trusted upstreams and limiting who can send queries to the affected resolver.
Event History
Frequently Asked Questions
What is the severity of CVE-2026-13321?
CVE-2026-13321 has a severity score of 8.6, categorized as high.
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.
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.
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.
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.