CVE-2026-78301 PUBLISHED

A malformed zone may contain an NS or DNAME node above its origin, which named treats as a zone cut. If an attacker inserts a malformed zone into a BIND authoritative server (e.g., via zone transfer), queries for names inside the configured zone then lose authoritative status and return an out-of-zone delegation. On a server that also provides recursion BIND can follow this locally sourced cut and cache attacker-supplied data, affecting names outside the configured zone. This situation persists as long as the malformed zone remains in the zone database. This issue affects BIND 9 versions 9.11.0 through 9.18.50, 9.20.0 through 9.20.27, 9.21.0 through 9.21.25, 9.11.3-S1 through 9.18.50-S1, and 9.20.9-S1 through 9.20.27-S1.

We are not aware of any active exploits.

No workarounds known.

Upgrade to the patched release most closely related to your current version of BIND 9: 9.20.29, 9.21.26, or 9.20.29-S1.

• ISC would like to thank Henrique Pereira for bringing this vulnerability to our attention.

• CVE-2026-78301
• https://downloads.isc.org/isc/bind9/9.20.29
• https://downloads.isc.org/isc/bind9/9.21.26

• CWE-349 Acceptance of Extraneous Untrusted Data With Trusted Data CWE

• In a successful attack on an authoritative server that is also a resolver, cache poisoning may occur with attacker supplied records. A purely authoritative server may return bogus attacker-supplied referrals to queries but without the AA flag.