CVE-2022-0396: DoS from specifically crafted TCP packets
  • 16 Mar 2022
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CVE-2022-0396: DoS from specifically crafted TCP packets

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Article Summary

CVE: CVE-2022-0396

Document version: 2.0

Posting date: 16 March 2022

Program impacted: BIND

Versions affected: BIND 9.16.11 -> 9.16.26, 9.17.0 -> 9.18.0 and versions 9.16.11-S1 -> 9.16.26-S1 of the BIND Supported Preview Edition.

Severity: Medium

Exploitable: Remotely


ISC recently discovered an issue in BIND that allows TCP connection slots to be consumed for an indefinite time frame via a specifically crafted TCP stream sent from a client. This issue is present in BIND 9.16.11 to 9.16.26 (including S editions), and 9.18.0.

This issue can only be triggered on BIND servers which have keep-response-order enabled, which is not the default configuration. The keep-response-order option is an ACL block; any hosts which are specified within it will be able to trigger this issue on affected versions.


Specifically crafted TCP streams can cause connections to BIND to remain in CLOSE_WAIT status for an indefinite period of time, even after the client has terminated the connection.

CVSS Score: 4.9


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


To mitigate this issue in all affected versions of BIND, use the default setting of keep-response-order { none; }.

Active exploits:

We are not aware of any active exploits.


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

  • 9.16.27
  • 9.18.1

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

  • 9.16.27-S1

Document revision history:

1.0 Early Notification, 9 March 2022
1.1 Grammatical edit to Description, 16 March 2022
2.0 Public disclosure, 16 March 2022

Related documents:

See CVE-2019-6477: TCP-pipelined queries can bypass tcp-clients limit for more information regarding CVE-2019-6477, in which ISC recommended setting keep-response-order to any to work around a previous issue where BIND was not respecting the TCP client limit.

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 at

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

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