CVE-2012-5166: Specially crafted DNS data can cause a lockup in named
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CVE-2012-5166: Specially crafted DNS data can cause a lockup in named

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Article Summary

A nameserver can be locked up if it can be induced to load a specially crafted combination of resource records.

CVE: CVE-2012-5166

Document version: 2.1

Posting date: 9 October 2012

Program impacted: BIND

Versions affected: 9.2.x -> 9.6.x, 9.4-ESV->9.4-ESV-R5-P1, 9.6-ESV->9.6-ESV-R7-P3, 9.7.0->9.7.6-P3, 9.8.0->9.8.3-P3, 9.9.0->9.9.1-P3

Severity: Critical

Exploitable: Remotely


If specific combinations of RDATA are loaded into a nameserver, either via cache or an authoritative zone, a subsequent query for a related record will cause named to lock up.

Please note: All versions of BIND 9.2, 9.3, 9.4, and 9.5 are also affected, but these branches are beyond their "end of life" (EOL) and no longer receive testing or security fixes from ISC. For current information on which versions are actively supported, please see


A nameserver that has become locked-up due to the problem reported in this advisory will not respond to queries or control commands. Normal functionality cannot be restored except by terminating and restarting named.

This vulnerability can be exploited remotely against recursive servers by inducing them to query for records provided by an authoritative server. It affects authoritative servers if one of the combinations of resource records is loaded from file, provided via zone transfer, or submitted to a zone via dynamic update.

CVSS Score: 7.8

CVSS Equation: (AV:N/AC:L/Au:N/C:N/I:N/A:C)

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

Workarounds: Setting the option 'minimal-responses' to 'yes' will prevent the lockup.

Active exploits: No known active exploits.

Solution: Upgrade to the patched version or new release most closely related to your current version of BIND. The patched versions of BIND and new releases can be downloaded from

  • BIND 9 version 9.7.7, 9.7.6-P4
  • BIND 9 version 9.6-ESV-R8, 9.6-ESV-R7-P4
  • BIND 9 version 9.8.4, 9.8.3-P4
  • BIND 9 version 9.9.2, 9.9.1-P4

Acknowledgement: ISC would like to thank Jake Montgomery of Dyn, Inc.

Document Revision History:

1.0 - Advance Notification to Phase 1, 1 October 2012
1.1 - Notification to Phase 3, 8 October 2012
2.0 - Notification to Phase 4 (Public), 9 October 2012
2.1 - Added Chinese translation. Added link to FAQ supplemental article in KB, 17 October 2012

Related Documents:

A Japanese translation of this document is available at:

A Spanish translation of this document is available at:

A Chinese translation of this document is available at:

If you'd like more information on ISC Subscription Support and Advance Security Notifications, please visit

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 security-officer@isc.orgTo 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:

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

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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