CVE-2015-5477: An error in handling TKEY queries can cause named to exit with a REQUIRE assertion failure
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CVE-2015-5477: An error in handling TKEY queries can cause named to exit with a REQUIRE assertion failure

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Article summary

A deliberately constructed packet can exploit an error in the handling of queries for TKEY records, permitting denial of service.

CVE: CVE-2015-5477

Document version: 2.2

Posting date: 28 July 2015

Program impacted: BIND

Versions affected: 9.1.0 -> 9.8.x, 9.9.0->9.9.7-P1, 9.10.0->9.10.2-P2

Severity: Critical

Exploitable: Remotely


An error in the handling of TKEY queries can be exploited by an attacker for use as a denial-of-service vector, as a constructed packet can use the defect to trigger a REQUIRE assertion failure, causing BIND to exit.


Both recursive and authoritative servers are vulnerable to this defect. Additionally, exposure is not prevented by either ACLs or configuration options limiting or denying service because the exploitable code occurs early in the packet handling, before checks enforcing those boundaries.

All versions of BIND 9 from BIND 9.1.0 (inclusive) through BIND 9.9.7-P1 and BIND 9.10.2-P2 are vulnerable.

Operators should take steps to upgrade to a patched version as soon as possible.

CVSS Score: 7.8

CVSS Vector: (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: None.

Active exploits: We have been informed that proof-of-concept code for an exploit has been published by a third party to a public source repository.

Solution: Upgrade to the patched release most closely related to your current version of BIND.  These can be downloaded from

  • BIND 9 version 9.9.7-P2
  • BIND 9 version 9.10.2-P3

Acknowledgements: ISC would like to thank Jonathan Foote for discovering and disclosing this vulnerability.

Document Revision History:

  • 1.0 Advance Notification, 21 July 2015
  • 2.0 Public Disclosure, 28 July 2015
  • 2.1 Added source code patch, 30 July 2015
  • 2.2 Updated the "Active Exploits" section to include the information that an exploit has been publicly disclosed, 1 August 2015

Related Documents:

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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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