CVE-2016-2776: Assertion Failure in buffer.c While Building Responses to a Specifically Constructed Request
- Updated on 04 Oct 2016
- 3 minutes to read
9.0.x -> 9.8.x, 9.9.0->9.9.9-P2, 9.9.3-S1->9.9.9-S3, 9.10.0->9.10.4-P2, 9.11.0a1->9.11.0rc1
Testing by ISC has uncovered a critical error condition which can occur when a nameserver is constructing a response. A defect in the rendering of messages into packets can cause named to exit with an assertion failure in buffer.c while constructing a response to a query that meets certain criteria.
This assertion can be triggered even if the apparent source address isn't allowed to make queries (i.e. doesn't match 'allow-query').
All servers are vulnerable if they can receive request packets from any source.
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&adv&version=2&vector=(AV:N/AC:L/Au:N/C:N/I:N/A:C)
No practical workarounds exist.
A step-by-step breakdown of the issue has been published and working Metasploit code is available. Crashes have been reported that appear to be the result active exploitation.
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 9.9.9-P3
- BIND 9 version 9.10.4-P3
- BIND 9 version 9.11.0rc3
BIND 9 Supported Preview edition is a feature preview version of BIND provided exclusively to eligible ISC Support customers.
- BIND 9 version 9.9.9-S5
Document Revision History: 1.0 2016-09-14 - Advance Notification 1.1 2016-09-21 - Added information about the Stable Preview release to versions affected. Updated solution section to reflect replacing 9.11.0rc2 with 9.11.0rc3 and 9.9.9-S4 with 9.9.9-S5. 2.0 2016-09-27 - Posting date changed and public disclosure. 2.1 2016-10-04 - Updated 'Active exploits' section.
See our BIND9 Security Vulnerability Matrix athttps://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/.
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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-00861/164/ISC-Software-Defect-and-Security-Vulnerability-Disclosure-Policy.html
This Knowledge Base article https://kb.isc.org/article/AA-01419 is the complete and official security advisory document.
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