CVE-2016-2775: A query name which is too long can cause a segmentation fault in lwresd
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CVE-2016-2775: A query name which is too long can cause a segmentation fault in lwresd

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Article Summary

Although not commonly used, the BIND 9 package contains provisions to allow systems to resolve names using the lightweight resolver protocol, a protocol similar to (but distinct from) the normal DNS protocols. The lightweight resolver protocol can be used either by running the lwresd utility installed with BIND 9, or by configuring named using the "lwres" statement in named.conf.

An error has been discovered in the BIND 9 implementation of the lightweight resolver protocol affecting systems which use this alternate method to do name resolution.

CVE: CVE-2016-2775

Document version: 2.0

Posting date: 18 July 2016

Program impacted: BIND

Versions affected: 9.0.x -> 9.9.9-P1, 9.10.0->9.10.4-P1, 9.11.0a3->9.11.0b1

Severity: Medium

Exploitable: Remotely (if lwresd is configured to accept remote client connections)


If the lightweight resolver is asked to resolve a query name which, when combined with a search list entry, exceeds the maximum allowable length, the server can terminate due to an error.


A server which is affected by this defect will terminate with a segmentation fault error, resulting in a denial of service to client programs attempting to resolve names.

CVSS Score: 5.4 if the server is configured to accept requests from the network.

CVSS Vector: (AV:N/AC:H/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:

Workarounds: None.

Active exploits: No known active exploits, but the bug has been publicly disclosed in an open bug repository operated by Red Hat.

Solution: Upgrade to the patched release most closely related to your current version of BIND. These can be downloaded from

  • BIND 9 version 9.9.9-P2
  • BIND 9 version 9.10.4-P2

The BIND 9.11 branch is currently in beta development.

  • BIND 9 version 9.11.0b2

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-S3

Document Revision History:

1.0 Advance Notification, 14 July 2016
2.0 Public Disclosure, 18 July 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

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's PGP key which can be found here: If you are unable to use encrypted email, you may also report new issues at:


ISC patches only currently supported versions. When possible we indicate EOL versions affected.  (For current information on which versions are actively supported, please see 

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.

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