BIND 9 vulnerability

What happened

If a BIND resolver is performing DNSSEC validation and encounters a maliciously crafted zone, the resolver may consume excessive CPU. Authoritative-only servers are generally unaffected, although there are circumstances where authoritative servers may make recursive queries (see: https://kb.isc.org/docs/why-does-my-authoritative-server-make-recursive-queries). This issue affects BIND 9 versions 9.11.0 through 9.16.50, 9.18.0 through 9.18.46, 9.20.0 through 9.20.20, 9.21.0 through 9.21.19, 9.11.3-S1 through 9.16.50-S1, 9.18.11-S1 through 9.18.46-S1, and 9.20.9-S1 through 9.20.20-S1.

Affected versions

BIND 9: 9.11.0 through 9.16.50 (custom); 9.18.0 through 9.18.46 (custom); 9.20.0 through 9.20.20 (custom); 9.21.0 through 9.21.19 (custom); 9.11.3-S1 through 9.16.50-S1 (custom); 9.18.11-S1 through 9.18.46-S1 (custom); 9.20.9-S1 through 9.20.20-S1 (custom) Fixed: See vendor advisory.

Why it matters

Review the vendor advisory and exposure of the affected product to determine operational impact.

Detection & mitigation

• Apply vendor-provided updates or mitigations.
• Review affected product exposure and access logs.