---
title: "CVE-2026-11605: Unnecessary validation of DNSSEC signed records"
slug: "cve-2026-11605"
description: "The issue is a resource exhaustion vulnerability associated with DNSSEC validation."
status: "new"
updated: 2026-07-22T12:20:21Z
published: 2026-07-22T12:20:21Z
canonical: "kb.isc.org/cve-2026-11605"
---

> ## Documentation Index
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# CVE-2026-11605: Unnecessary validation of DNSSEC signed records

**CVE:** [CVE-2026-11605](https://www.cve.org/CVERecord?id=CVE-2026-11605)

**Title:** Unnecessary validation of DNSSEC signed records

**Document version:** 2.0

**Posting date:** 22 July 2026

**Program impacted:** [BIND 9](https://www.isc.org/bind/)

**Versions affected:**

BIND

- 9.20.0 -> 9.20.24
- 9.21.0 -> 9.21.23

BIND Supported Preview Edition

- 9.20.9-S1 -> 9.20.24-S1

**Severity:** High

**Exploitable:** Remotely

**Description:**

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.

**Impact:**

Exhaustion of CPU resources.

**CVSS Score:** 7.5

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

For more information on the Common Vulnerability Scoring System and to obtain your specific environmental score please visit: [https://nvd.nist.gov/vuln-metrics/cvss/v3-calculator?vector=AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H&version=3.1](https://nvd.nist.gov/vuln-metrics/cvss/v3-calculator?vector=AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H&version=3.1).

**Workarounds:**

No workarounds known.

**Active exploits:**

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

**Solution:**

Upgrade to the patched release most closely related to your current version of BIND 9:

- 9.20.26
- 9.21.24

BIND Supported Preview Edition is a special feature preview branch of BIND provided to eligible ISC support customers.

- 9.20.26-S1

**Document revision history:**

- 1.0 Early Notification, 15 July 2026
- 1.1 Revised the list of fixed versions, 20 July 2026
- 2.0 Public disclosure, 22 July 2026

**Related documents:**

See our [BIND 9 Security Vulnerability Matrix](https://kb.isc.org/docs/aa-00913) for a complete listing of security vulnerabilities and versions affected.

**Do you still have questions?**

Questions regarding this advisory should be posted as confidential GitLab issues at:

[https://gitlab.isc.org/isc-projects/bind9/-/issues/new?issue[confidential]=true](https://gitlab.isc.org/isc-projects/bind9/-/issues/new?issue%5Bconfidential%5D=true)

**Note:**

ISC patches only currently supported versions. When possible we indicate EOL versions affected. For current information on which versions are actively supported, please see [https://www.isc.org/download/](https://www.isc.org/download/).

**ISC Security Vulnerability Disclosure Policy:**

Details of our current security advisory policy and practice can be found in the ISC Software Defect and Security Vulnerability Disclosure Policy at [https://kb.isc.org/docs/aa-00861](https://kb.isc.org/docs/aa-00861).

The Knowledgebase article [https://kb.isc.org/docs/cve-2026-11605](https://kb.isc.org/docs/cve-2026-11605) is the complete and official security advisory document.

**Legal Disclaimer:**

Internet Systems Consortium (ISC) is providing this notice on an "AS IS" basis. No warranty or guarantee of any kind is expressed in this notice and none should be implied. ISC expressly excludes and disclaims any warranties regarding this notice or materials referred to in this notice, including, without limitation, any implied warranty of merchantability, fitness for a particular purpose, absence of hidden defects, or of non-infringement. Your use or reliance on this notice or materials referred to in this notice is at your own risk. ISC may change this notice at any time. A stand-alone copy or paraphrase of the text of this document that omits the document URL is an uncontrolled copy. Uncontrolled copies may lack important information, be out of date, or contain factual errors.