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.

Description:

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.

Impact:

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: https://nvd.nist.gov/cvss.cfm?calculator&version=2&vector=(AV:N/AC:L/Au:N/C:N/I:N/A:C)

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 http://www.isc.org/downloads.

• BIND 9 version 9.9.7-P2
• BIND 9 version 9.10.2-P3
• The attached patch can probably be applied to the source code for any vulnerable version of BIND 9.
  

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:

See our BIND9 Security Vulnerability Matrix at https://kb.isc.org/article/AA-00913 for a complete listing of Security Vulnerabilities and versions affected.

If you'd like more information on ISC Subscription Support and Advance Security Notifications, please visit http://www.isc.org/services

Do you still have questions?  Questions regarding this advisory should go to security-officer@isc.org.  To report a new issue, please encrypt your message using security-officer@isc.org's PGP key which can be found here: https://www.isc.org/downloads/software-support-policy/openpgp-key/.  If you are unable to use encrypted email, you may also report new issues at: https://www.isc.org/community/report-bug/.

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 http://www.isc.org/downloads/). 

ISC Security Vulnerability Disclosure Policy:  Details of our current security advisory policy and practice can be found here: https://kb.isc.org/article/AA-00861/164/ISC-Software-Defect-and-Security-Vulnerability-Disclosure-Policy.html

This Knowledge Base article https://kb.isc.org/article/AA-01272 is the complete and official security advisory document.

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