CVE-2014-8500: A Defect in Delegation Handling Can Be Exploited to Crash BIND

AA-01216

Failure to place limits on delegation chaining can allow an attacker to crash BIND or cause memory exhaustion.

Document Version:        
2.0
Posting date: 
08 December 2014
Program Impacted: 
BIND 9
Versions affected: 
9.0.x -> 9.8.x, 9.9.0 -> 9.9.6, 9.10.0 -> 9.10.1
Severity: 
Critical
Exploitable: 
Remotely

Description:

By making use of maliciously-constructed zones or a rogue server, an attacker can exploit an oversight in the code BIND 9 uses to follow delegations in the Domain Name Service, causing BIND to issue unlimited queries in an attempt to follow the delegation.  This can lead to resource exhaustion and denial of service (up to and including termination of the named server process.)

Impact:

All recursive resolvers are affected.  Authoritative servers can be affected if an attacker can control a delegation traversed by the authoritative server in servicing the zone.

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

Workarounds:

No workarounds exist.  Vulnerable versions of BIND 9 should be upgraded.

Active exploits:

No known active exploits.

Solution:  Upgrade to the patched release most closely related to your current version of BIND.  Patched builds of currently supported branches of BIND (9.9 and 9.10) can be downloaded via http://www.isc.org/downloads

  • BIND 9 version 9.9.6-P1
  • BIND 9 version 9.10.1-P1
Regarding older versions:
  • BIND 9.6-ESV and BIND 9.8 have been officially designated "end of life" (EOL) and no longer receive support.  All organizations running EOL branches should be planning transition to currently supported branches.  However, due to the severity of this particular issue, source code diffs which can be applied to BIND 9.8 and BIND 9.6-ESV will be made available on request to security-officer@isc.org.

Acknowledgements: ISC would like to thank Florian Maury (ANSSI) for discovering and reporting this vulnerability.

Document Revision History:

1.0 Advance Notification: 20 November 2014 
2.0 Public Disclosure: 08 December 2014

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/support/.

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: http://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-01216 is the complete and official security advisory document.

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