--- title: "CVE-2023-2828" slug: "cve-2023-2828" description: "CVE-2023-2828: By exploiting a specific flaw, an attacker can cause the amount of memory used by a named resolver to go well beyond the configured max-cache-size limit. The effectiveness of the attack depends on a number of factors (e.g. query load, query patterns), but since the default value of the max-cache-size statement is 90%, in the worst case the attacker can exhaust all available memory on the host running named, leading to a denial-of-service condition." updated: 2023-06-21T13:51:02Z published: 2023-06-21T13:51:02Z --- > ## 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-2023-2828: named's configured cache size limit can be significantly exceeded **CVE:** [CVE-2023-2828](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-2828) **Document version:** 2.0 **Posting date:** 21 June 2023 **Program impacted:** [BIND 9](https://www.isc.org/bind/) **Versions affected:** BIND - 9.11.0 -> 9.16.41 - 9.18.0 -> 9.18.15 - 9.19.0 -> 9.19.13 BIND Supported Preview Edition - 9.11.3-S1 -> 9.16.41-S1 - 9.18.11-S1 -> 9.18.15-S1 (Versions prior to 9.11.37 & 9.11.37-S1 were not assessed, but we believe that all versions of BIND 9.11 are vulnerable. Some even older major branches may be vulnerable as well.) **Severity:** High **Exploitable:** Remotely **Description:** Every `named` instance configured to run as a recursive resolver maintains a cache database holding the responses to the queries it has recently sent to authoritative servers. The size limit for that cache database can be configured using the `max-cache-size` statement in the configuration file; it defaults to 90% of the total amount of memory available on the host. When the size of the cache reaches 7/8 of the configured limit, a cache-cleaning algorithm starts to remove expired and/or least-recently used RRsets from the cache, to keep memory use below the configured limit. It has been discovered that the effectiveness of the cache-cleaning algorithm used in `named` can be severely diminished by querying the resolver for specific RRsets in a certain order, effectively allowing the configured `max-cache-size` limit to be significantly exceeded. **Impact:** By exploiting this flaw, an attacker can cause the amount of memory used by a `named` resolver to go well beyond the configured `max-cache-size` limit. The effectiveness of the attack depends on a number of factors (e.g. query load, query patterns), but since the default value of the `max-cache-size` statement is `90%`, in the worst case the attacker can exhaust all available memory on the host running `named`, leading to a denial-of-service condition. **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:** We are not aware of any active exploits. **Solution:** Upgrade to the patched release most closely related to your current version of BIND 9: - 9.16.42 - 9.18.16 - 9.19.14 BIND Supported Preview Edition is a special feature preview branch of BIND provided to eligible ISC support customers. - 9.16.42-S1 - 9.18.16-S1 **Acknowledgments:** ISC would like to thank Shoham Danino from Reichman University, Anat Bremler-Barr from Tel-Aviv University, Yehuda Afek from Tel-Aviv University, and Yuval Shavitt from Tel-Aviv University for bringing this vulnerability to our attention. **Document revision history:** - 1.0 Early Notification, 14 June 2023 - 2.0 Public disclosure, 21 June 2023 **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 [security-officer@isc.org](mailto:security-officer@isc.org). *To report a new issue, please encrypt your message using security-officer@isc.org's PGP key, which can be found here: [https://www.isc.org/pgpkey/](https://www.isc.org/pgpkey/). If you are unable to use encrypted email you may also report new issues at: [https://www.isc.org/reportbug/](https://www.isc.org/reportbug/).* **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-2023-2828](https://kb.isc.org/docs/cve-2023-2828) 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.