CVE-2026-5946: ISC BIND

High severity, CVSS 7.5. EPSS: 1.7% chance of exploitation in the next 30 days.

Multiple flaws have been identified in `named` related to the handling of DNS messages whose CLASS is not Internet (`IN`) — for example, `CHAOS` or `HESIOD`, or DNS messages that specify meta-classes (`ANY` or `NONE`) in the question section. Specially crafted requests reaching the affected code paths — recursion, dynamic updates (`UPDATE`), zone change notifications (`NOTIFY`), or processing of `IN`-specific record types in non-`IN` data — can cause assertion failures in `named`. This issue affects BIND 9 versions 9.11.0 through 9.16.50, 9.18.0 through 9.18.48, 9.20.0 through 9.20.22, 9.21.0 through 9.21.21, 9.11.3-S1 through 9.16.50-S1, 9.18.11-S1 through 9.18.48-S1, and 9.20.9-S1 through 9.20.22-S1.

Affected products

• ISC BIND: from 9.11.0, up to and including 9.16.50; from 9.18.0, before 9.18.49 (fixed in 9.18.49); from 9.20.0, before 9.20.23 (fixed in 9.20.23); from 9.21.0, before 9.21.22 (fixed in 9.21.22)

Published 2026-05-20. Last modified 2026-09-17.