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

Michael McNally mcnally at
Mon Jul 18 23:57:33 UTC 2016

Although not commonly used, the BIND 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 or by configuring
named using the "lwres" statement in named.conf.

An error has been discovered in the BIND 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 (lwres only)
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 lwres 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)

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Active exploits:

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


   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 BIND9 Security Vulnerability Matrix at for a complete listing of
   Security Vulnerabilities and versions affected.

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