CVE-2016-2088: A response containing multiple DNS cookies causes servers with cookie support enabled to exit with an assertion failure
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CVE-2016-2088: A response containing multiple DNS cookies causes servers with cookie support enabled to exit with an assertion failure

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Article Summary

CVE: CVE-2016-2088

Document version: 2.0

Posting date: 09 March 2016

Program impacted: BIND

Versions affected: 9.10.0 -> 9.10.3-P3

Severity: High

Exploitable: Remotely

Description:

BIND 9.10 has preliminary support for DNS cookies (or source identity tokens), a proposed mechanism designed to allow lightweight transaction security between a querying party and a nameserver. An error in the BIND code implementing support for this optional feature permits a deliberately misconstructed packet containing multiple cookie options to cause named to terminate with an INSIST assertion failure in resolver.c if DNS cookie support is enabled in the server. Only servers with DNS cookie support enabled at build time can be affected by this defect; in servers which do not have DNS cookie support selected, any cookies encountered will be ignored as unknown option types.

Impact:

Servers which are built with DNS cookie support enabled are vulnerable to denial of service if an attacker can cause them to receive and process a response that contains multiple cookie options.

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:

Servers which do not have cookie support included are not at risk from this vulnerability.

When BIND 9.10 is built from ISC-supported source, cookie support is not selected by default. To be included, it must be elected using the "--enable-sit" command-line argument when running the "configure" script in the top level source directory. Operators with affected servers can reconfigure and rebuild BIND without cookie support if they prefer not to upgrade to a release containing the fix. However, ISC-provided binary packages for Windows do have "--enable-sit" selected. Server operators using the Windows binary packages should upgrade to the corrected version.

Active exploits: No known active exploits.

Solution: Reconfigure and rebuild BIND without enabling cookie support or upgrade to the patched release most closely related to your current version of BIND. 

  • BIND 9 version 9.10.3-P4

Document Revision History:

1.0 Advance Notification 02 March 2016
2.0 Public Disclosure 09 March 2016

Related Documents: See our BIND 9 Security Vulnerability Matrix 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 https://www.isc.org/support/.

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 https://www.isc.org/downloads/). 

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.

Legal Disclaimer:

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