CVE-2015-5722: Parsing malformed keys may cause BIND to exit due to a failed assertion in buffer.c

Document Version:        2.0
Posting date:  2 September 2015
Program Impacted:  BIND
Versions affected: BIND 9.0.0 -> 9.8.8,  BIND 9.9.0 -> 9.9.7-P2, BIND 9.10.0 -> 9.10.2-P3
Severity:  Critical
Exploitable:  Remotely

Description:

Parsing a malformed DNSSEC key can cause a validating resolver to exit due to a failed assertion in buffer.c.  It is possible for a remote attacker to deliberately trigger this condition, for example by using a query which requires a response from a zone containing a deliberately malformed key.

Impact:

Recursive servers are at greatest risk but an authoritative server could be affected if an attacker controls a zone the server must query against to perform its zone service.

Servers which are affected may terminate with an assertion failure, causing denial of service to all clients.

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 are not performing validation are not at risk from this defect (but are at increased risk from other types of DNS attack.)  ISC does not recommend disabling validation to deal with this issue; upgrading to a fixed version is the preferred solution.

Active exploits: 

None known

Solution:

Upgrade to the patched release most closely related to your current version of BIND. These can all be downloaded from http://www.isc.org/downloads.

  • BIND 9 version 9.9.7-P3
  • BIND 9 version 9.10.2-P4

BIND development releases scheduled to be published at the same time as the public disclosure of this vulnerability will also contain the fix for this security issue.

  • BIND 9 version 9.9.8rc1
  • BIND 9 version 9.10.3rc1

Acknowledgements:

ISC would like to thank Hanno Böck from the Fuzzing Project for discovering and reporting this defect.  We would also like to express our appreciation to the developers of the American Fuzzy Lop tool, which has been instrumental in revealing recently-disclosed vulnerabilities in BIND.

Document Revision History:

1.0 Advance Notification 19 August 2015
1.1 “Versions affected” information clarified  24 August, 2015
2.0 Public Disclosure  2 September, 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/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 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-01287 is the complete and official security advisory document.

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Last modified: September 2, 2015 at 12:41 pm