ISC BIND up to 9.20.24/9.20.24-S1/9.21.23 DNSSEC Validation resource consumption

Summaryinfo

A vulnerability has been found in ISC BIND up to 9.20.24/9.20.24-S1/9.21.23 and classified as critical. This affects an unknown function of the component DNSSEC Validation. This manipulation causes resource consumption. This vulnerability is tracked as CVE-2026-11605. The attack is possible to be carried out remotely. No exploit exists.

Detailsinfo

A vulnerability classified as critical was found in ISC BIND up to 9.20.24/9.20.24-S1/9.21.23. Affected by this vulnerability is an unknown part of the component DNSSEC Validation. The manipulation with an unknown input leads to a resource consumption vulnerability. The CWE definition for the vulnerability is CWE-400. The product does not properly control the allocation and maintenance of a limited resource, thereby enabling an actor to influence the amount of resources consumed, eventually leading to the exhaustion of available resources. As an impact it is known to affect availability. The summary by CVE is:

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.

The advisory is shared at kb.isc.org. This vulnerability is known as CVE-2026-11605 since 06/08/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Neither technical details nor an exploit are publicly available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 07/22/2026). MITRE ATT&CK project uses the attack technique T1499 for this issue.

Upgrading to version 9.20.24, 9.20.24-S1 or 9.21.23 eliminates this vulnerability.

If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Productinfo

Type

• Domain Name Software

Vendor

• ISC

Name

• BIND

Version

• 9.20.0
• 9.20.1
• 9.20.2
• 9.20.3
• 9.20.4
• 9.20.5
• 9.20.6
• 9.20.7
• 9.20.8
• 9.20.9
• 9.20.10
• 9.20.11
• 9.20.12
• 9.20.13
• 9.20.14
• 9.20.15
• 9.20.16
• 9.20.17
• 9.20.18
• 9.20.19
• 9.20.20
• 9.20.21
• 9.20.22
• 9.20.23
• 9.20.24
• 9.20.24-S1
• 9.21.0
• 9.21.1
• 9.21.2
• 9.21.3
• 9.21.4
• 9.21.5
• 9.21.6
• 9.21.7
• 9.21.8
• 9.21.9
• 9.21.10
• 9.21.11
• 9.21.12
• 9.21.13
• 9.21.14
• 9.21.15
• 9.21.16
• 9.21.17
• 9.21.18
• 9.21.19
• 9.21.20
• 9.21.21
• 9.21.22
• 9.21.23

License

• open-source

Website

• Vendor: https://www.isc.org/

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