High · published March 25, 2026
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.
| Product | Versions | Fixed in |
|---|---|---|
| isc/bind | ≥ 9.11.0, ≤ 9.16.50 | — |
| isc/bind | ≥ 9.18.0, < 9.18.47 | 9.18.47 |
| isc/bind | ≥ 9.20.0, < 9.20.21 | 9.20.21 |
| isc/bind | ≥ 9.21.0, < 9.21.20 | 9.21.20 |