CVE-2023-5680: Cleaning an ECS-enabled cache may cause excessive CPU load
  • 13 Feb 2024
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CVE-2023-5680: Cleaning an ECS-enabled cache may cause excessive CPU load

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Article Summary

CVE: CVE-2023-5680

Title: Cleaning an ECS-enabled cache may cause excessive CPU load

Document version: 2.0

Posting date: 13 February 2024

Program impacted: BIND 9

Versions affected:

BIND Supported Preview Edition

  • 9.11.3-S1 -> 9.11.37-S1
  • 9.16.8-S1 -> 9.16.45-S1
  • 9.18.11-S1 -> 9.18.21-S1

(Versions prior to 9.11.37-S1 were not assessed.)

Severity: Medium

Exploitable: Remotely


If a resolver cache has a very large number of ECS records stored for the same name, the process of cleaning the cache database node for this name can significantly impair query performance.


By sending specific queries to a resolver, an attacker can degrade named's query-handling performance. In the worst-case scenario, a resolver can become entirely unresponsive.

CVSS Score: 5.3


For more information on the Common Vulnerability Scoring System and to obtain your specific environmental score please visit:


There is no workaround for this issue other than disabling the ECS feature entirely.

Active exploits:

We are not aware of any active exploits.


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

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


ISC would like to thank Yann Kerherve and Ask Bjørn Hansen for bringing this vulnerability to our attention.

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 for a complete listing of security vulnerabilities and versions affected.

Do you still have questions? Questions regarding this advisory should be mailed to or posted as confidential GitLab issues at[confidential]=true.


ISC patches only currently supported versions. When possible we indicate EOL versions affected. For current information on which versions are actively supported, please see

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

The Knowledgebase article is the complete and official security advisory document.

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