CVE-2019-6469: BIND Supported Preview Edition can exit with an assertion failure if ECS is in use
  • 30 May 2019
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CVE-2019-6469: BIND Supported Preview Edition can exit with an assertion failure if ECS is in use

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Article summary

CVE: CVE-2019-6469

Document version: 2.0

Posting date: 29 May 2019

Program impacted: BIND

Versions affected: BIND Supported Preview Edition version 9.10.5-S1 -> 9.11.6-S1. ONLY BIND Supported Preview Edition releases are affected.

Severity: Medium

Exploitable: Remotely


An error in the EDNS Client Subnet (ECS) feature for recursive resolvers can cause BIND to exit with an assertion failure when processing a response that has malformed RRSIGs.


An attacker who is able to cause a server to perform a query whose answer will be accompanied by malformed RRSIGs can deliberately cause a server to exit if it is using the recursive ECS feature.

CVSS Score: 5.9


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


Only servers which have enabled the EDNS Client Subnet (ECS) feature can be affected by this defect; it can be prevented by disabling ECS options in the server's configuration.

Active exploits:

None known.


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

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

  • BIND 9.11.7-S1

Acknowledgements: ISC would like to thank Quad9 for reporting this issue.

Document revision history:

1.0 Early Notification, 15 May 2019
2.0 Public Disclosure, 29 May 2019

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 go to To report a new issue, please encrypt your message using's PGP key which can be found here: If you are unable to use encrypted email, you may also report new issues at:


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.

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

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