# CVE-2026-11605: ISC BIND 9 resource exhaustion in DNSSEC validation

Source: https://junglewise.ai/threats/cve-2026-11605-isc-bind-9-resource-exhaustion-in-dnssec-validation  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-22. Updated: 2026-07-22  
License: CC BY 4.0 with a link back

CVE-2026-11605 · Severity: high · CVSS 7.5 · Published 2026-07-22

A resource exhaustion vulnerability exists in BIND 9, a widely used software for translating domain names into IP addresses. An attacker can send a specially crafted DNS query that forces the server to perform excessive and unnecessary security checks, consuming high amounts of CPU power. This can lead to a denial-of-service, making the DNS server slow or completely unresponsive to legitimate user requests.

Technologies: [Isc BIND 9](https://junglewise.ai/threats/technologies/bind-9). Vendors: [Isc](https://junglewise.ai/threats/vendors/isc).

## Quick answers

**Is CVE-2026-11605 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-11605 being exploited in the wild.

**How severe is CVE-2026-11605?** High severity, with a CVSS score of 7.5, published 22 July 2026.

**Which products and versions are affected?** Isc BIND 9 9.20.0 through 9.20.24, 9.21.0 through 9.21.23, 9.20.9-S1 through 9.20.24-S1.

**Is there a fix for CVE-2026-11605?** A patch was published on 2026-07-22: Patched versions 9.20.26 and 9.21.24 released Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-11605 attacked?** It is attacked over the network, in a hosted service.

**Am I affected by CVE-2026-11605?** Check whether you run Isc BIND 9 at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A resource exhaustion vulnerability exists in BIND 9's DNSSEC validation logic. The resolver incorrectly attempts to validate all RRSIG records provided in an answer, even those that are not required for a successful validation. By querying an authoritative server that returns a large number of valid but unnecessary RRSIG records, a remote attacker can cause the BIND validator to consume disproportionate CPU resources. This is classified as an early amplification/incorrect behavior order issue (CWE-408). Patches are available in versions 9.20.26, 9.21.24, and 9.20.26-S1.

## Affected products

- ISC BIND 9 9.20.0 through 9.20.24, 9.21.0 through 9.21.23, 9.20.9-S1 through 9.20.24-S1

## Timeline

- 2026-07-15: other: Early notification provided
- 2026-07-22: disclosed: Public disclosure
- 2026-07-22: patched: Patched versions 9.20.26 and 9.21.24 released

## References

- [https://downloads.isc.org/isc/bind9/9.20.26](https://downloads.isc.org/isc/bind9/9.20.26)
- [https://downloads.isc.org/isc/bind9/9.21.24](https://downloads.isc.org/isc/bind9/9.21.24)
- [https://kb.isc.org/docs/cve-2026-11605](https://kb.isc.org/docs/cve-2026-11605)

## Related threats

- [ISC BIND recursive server assert failure denial of service](https://junglewise.ai/threats/cve-2026-97313-a-recursive-bind-server-that-receives-a-query-with-recursion)
- [ISC BIND DNSSEC validation bypass in NSEC records](https://junglewise.ai/threats/cve-2026-13321-isc-bind-dnssec-validation-bypass-in-nsec-records)
- [ISC BIND 9 denial of service via NSEC and NSEC3 assertion failure](https://junglewise.ai/threats/cve-2026-13204-isc-bind-9-denial-of-service-via-nsec-and-nsec3-assertion-failure)
- [ISC BIND 9 denial of service via CNAME or DNAME record ordering](https://junglewise.ai/threats/cve-2026-12617-isc-bind-9-denial-of-service-via-cname-or-dname-record-ordering)
- [ISC BIND 9 cache poisoning via RRSIG label count discrepancy](https://junglewise.ai/threats/cve-2026-11721-isc-bind-9-cache-poisoning-via-rrsig-label-count-discrepancy)