CVE-2026-11605 PUBLISHED

Unnecessary validation of DNSSEC signed records

Assigner: isc
Reserved: 08.06.2026 Published: 22.07.2026 Updated: 22.07.2026

The issue is a resource exhaustion vulnerability associated with DNSSEC validation. BIND always validates all RRSIG records in an answer, even if they are not strictly needed. A query to an authoritative server/zone which returns many valid but superfluous RRSIG records causes the validator to waste disproportionate CPU time. This issue affects BIND 9 versions 9.20.0 through 9.20.24, 9.21.0 through 9.21.23, and 9.20.9-S1 through 9.20.24-S1.

Metrics

CVSS 3.1

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS Score: 7.5

Attack Vector	Network	Scope	Unchanged
Attack Complexity	Low	Confidentiality Impact	None
Privileges Required	None	Integrity Impact	None
User Interaction	None	Availability Impact	High

CVSS 3.1

Product Status

Vendor	ISC
Product	BIND 9
Versions	Default: unaffected affected from 9.20.0 to 9.20.24 (incl.) affected from 9.21.0 to 9.21.23 (incl.) affected from 9.20.9-S1 to 9.20.24-S1 (incl.)

Exploits

This flaw was discovered in internal testing. We are not aware of any active exploits.

Workarounds

No workarounds known.

Solutions

Upgrade to the patched release most closely related to your current version of BIND 9: 9.20.26, 9.21.24, or 9.20.26-S1.