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

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

Document Version:          2.0
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:



Active exploits: 

None known.

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

Related Documents:

See our BIND9 Security Vulnerability Matrix at for a complete listing of Security Vulnerabilities and versions affected.

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Last modified: July 28, 2015 at 12:56 pm