--- title: "CVE-2023-5517" slug: "cve-2023-5517" description: "A flaw in query-handling code can cause named to exit prematurely with an assertion failure when nxdomain-redirect ; is configured, and the resolver receives a PTR query for an RFC 1918 address that would normally result in an authoritative NXDOMAIN response." status: "new" updated: 2024-02-13T13:22:34Z published: 2024-02-13T13:22:34Z --- > ## Documentation Index > Fetch the complete documentation index at: https://kb.isc.org/llms.txt > Use this file to discover all available pages before exploring further. # CVE-2023-5517: Querying RFC 1918 reverse zones may cause an assertion failure when nxdomain-redirect is enabled **CVE:** [CVE-2023-5517](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-5517) **Title:** Querying RFC 1918 reverse zones may cause an assertion failure when "nxdomain-redirect" is enabled **Document version:** 2.0 **Posting date:** 13 February 2024 **Program impacted:** [BIND 9](https://www.isc.org/bind/) **Versions affected:** BIND - 9.12.0 -> 9.16.45 - 9.18.0 -> 9.18.21 - 9.19.0 -> 9.19.19 BIND Supported Preview Edition - 9.16.8-S1 -> 9.16.45-S1 - 9.18.11-S1 -> 9.18.21-S1 **Severity:** High **Exploitable:** Remotely **Description:** A flaw in query-handling code can cause `named` to exit prematurely with an assertion failure when: - `nxdomain-redirect <domain>;` is configured, and - the resolver receives a PTR query for an RFC 1918 address that would normally result in an authoritative NXDOMAIN response. **Impact:** If both of the above conditions are met, a single suitable query will cause `named` to crash. **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:** Disabling the `nxdomain-redirect` feature makes the faulty code path impossible to reach, preventing this flaw from being exploitable. **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: - 9.16.48 - 9.18.24 - 9.19.21 BIND Supported Preview Edition is a special feature preview branch of BIND provided to eligible ISC support customers. - 9.16.48-S1 - 9.18.24-S1 **Document revision history:** - 1.0 Early Notification, 10 January 2024 - 1.1 Revised Early Notification, 15 January 2024 - 1.2 Revised the list of fixed versions, 11 February 2024 - 2.0 Public disclosure, 13 February 2024 **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 mailed to [bind-security@isc.org](mailto:bind-security@isc.org) or 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-2023-5517](https://kb.isc.org/docs/cve-2023-5517) 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.