Executive brief
BIND is a widely-used DNS resolver software that translates domain names into IP addresses for internet connectivity. On resolvers configured with the dns64 feature (used for IPv6/IPv4 translation), a specially crafted malformed DNS response from an authoritative server can cause the BIND process to crash unexpectedly, resulting in a complete service outage and loss of DNS resolution capability for affected clients.
Technical details
This is a denial-of-service vulnerability in BIND's dns64 functionality. When a resolver processes a malformed DNS answer from an authoritative server—specifically one that is malformed in a particular way—and dns64 is enabled, the named process crashes without proper error handling. The vulnerability is triggered by parsing a network-reachable response from an authoritative DNS server; no authentication or special client privileges are required. The attack vector is network-based, and an attacker can cause service disruption by controlling or spoofing responses from an authoritative server. Patches are available in BIND 9.18.51, 9.20.28, 9.20.28-S2, and 9.21.26.
Affected products
- ISC BIND 9.11.0–9.18.50, 9.11.3-S1–9.18.50-S1, 9.20.0–9.20.27, 9.20.9-S1–9.20.27-S1, 9.21.0–9.21.25
Timeline
- 2026-09-16: disclosed
- 2026-09-16: patched: Patches released: BIND 9.18.51, 9.20.28, 9.20.28-S2, 9.21.26