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CVE-2015-5477: An error in handling TKEY queries can cause named to exit with a REQUIRE assertion failure
Author: Michael McNally Reference Number: AA-01272 Views: 154116 Created: 2015-07-28 10:00 Last Updated: 2016-04-18 23:30 90 Rating/ 5 Voters

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

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

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.orgTo 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.

Legal Disclaimer:
Internet Systems Consortium (ISC) is providing this notice on an "AS IS" basis. No warranty or guarantee of any kind is expressed in this notice and none should be implied. ISC expressly excludes and disclaims any warranties regarding this notice or materials referred to in this notice, including, without limitation, any implied warranty of merchantability, fitness for a particular purpose, absence of hidden defects, or of non-infringement. Your use or reliance on this notice or materials referred to in this notice is at your own risk. ISC may change this notice at any time.  A stand-alone copy or paraphrase of the text of this document that omits the document URL is an uncontrolled copy. Uncontrolled copies may lack important information, be out of date, or contain factual errors.


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