---
title: "CVE-2026-94300: Concurrent GSS-TSIG messages corrupt memory"
slug: "cve-2026-94300"
updated: 2026-10-21T12:30:55Z
published: 2026-10-21T12:30:55Z
canonical: "kb.isc.org/cve-2026-94300"
---

> ## Documentation Index
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# CVE-2026-94300: Concurrent GSS-TSIG messages corrupt memory

**CVE:** [CVE-2026-94300](https://www.cve.org/CVERecord?id=CVE-2026-94300)

**Title:** Concurrent GSS-TSIG messages corrupt memory

**Document version:** 2.0

**Posting date:** 21 October 2026

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

**Versions affected:**

BIND

- 9.11.0 -> 9.18.50
- 9.20.0 -> 9.20.29
- 9.21.0 -> 9.21.26

BIND Supported Preview Edition

- 9.11.3-S1 -> 9.18.50-S1
- 9.20.9-S1 -> 9.20.29-S1

**Severity:** High

**Exploitable:** Remotely

**Description:**

Replaying GSS-TSIG signed UDP messages can result in memory corruption in "`named`". An attacker who can capture a previously signed UDP message can replay it while the negotiated TSIG key is still valid. By also sending crafted queries to a zone the attacker controls, the attacker may potentially achieve remote code execution.

**Impact:**

Memory corruption, leading to program abort and/or potential remote code execution.

**CVSS Score:** 8.1

**CVSS Vector:** CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/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:H/PR:N/UI:N/S:U/C:H/I:H/A:H&version=3.1](https://nvd.nist.gov/vuln-metrics/cvss/v3-calculator?vector=AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H&version=3.1).

**Workarounds:**

No workarounds known.

**Active exploits:**

We are not aware of any active exploits.

**Solution:**

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

- 9.20.30
- 9.21.27

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

- 9.20.30-S1

**Acknowledgments:**

While this flaw was discovered in internal testing, ISC would like to thank Dave Aitel from OpenAI who independently discovered and responsibly reported the issue to ISC.

**Document revision history:**

- 1.0 Early Notification, 14 October 2026
- 2.0 Public disclosure, 21 October 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-2026-94300](https://kb.isc.org/docs/cve-2026-94300) 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.