CVE-2026-78301: ISC BIND 9

Medium severity, CVSS 5.8. EPSS: 0.2% chance of exploitation in the next 30 days.

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.

Affected products

• ISC BIND 9: from 9.11.0, up to and including 9.18.50; from 9.20.0, up to and including 9.20.27; from 9.21.0, up to and including 9.21.25; from 9.11.3-S1, up to and including 9.18.50-S1; from 9.20.9-S1, up to and including 9.20.27-S1

Published 2026-09-16. Last modified 2026-09-17.