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

[Michael McNally]

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

CVE:                      CVE-2014-8500
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 at 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.

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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

This Knowledge Base article https://kb.isc.org/article/AA-01216 is
the complete and official security advisory document.

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