CVE-2017-3138: named exits with a REQUIRE assertion failure if it receives a null command string on its control channel
mcnally at isc.org
Thu Apr 13 00:03:59 UTC 2017
Document Version: 2.0
Posting date: 12 April 2017
Program Impacted: BIND
Versions affected: 9.9.9->9.9.9-P7, 9.9.10b1->9.9.10rc2,
Exploitable: Remotely, from hosts that are within the ACL permitted
access to the control channel
named contains a feature which allows operators to issue commands
to a running server by communicating with the server process
over a control channel, using a utility program such as rndc.
A regression introduced in a recent feature change has created
a situation under which some versions of named can be caused
to exit with a REQUIRE assertion failure if they are sent a
null command string.
The BIND control channel is not configured by default, but when
configured will accept commands from those IP addresses that
are specified in its access control list and/or from clients
which present the proper transaction key. Using this defect,
an attacker can cause a running server to stop if they can get
it to accept control channel input from them. In most instances
this is not as bad as it sounds, because existing commands
permitted over the control channel (i.e. "rndc stop") can already
be given to cause the server to stop.
However, BIND 9.11.0 introduced a new option to allow "read
only" commands over the command channel. Using this restriction,
a server can be configured to limit specified clients to giving
control channel commands which return information only (e.g.
"rndc status") without affecting the operational state of the
server. The defect described in this advisory, however, is not
properly stopped by the "read only" restriction, in essence
permitting a privilege escalation allowing a client which should
only be permitted the limited set of "read only" operations to
cause the server to stop execution.
CVSS Score: 6.5
CVSS Vector: CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
For more information on the Common Vulnerability Scoring System and
to obtain your specific environmental score please visit:
None. However, in a properly configured server, access to the
control channel should already be limited by either network
ACLs, TSIG keys, or both.
No known active exploits
Upgrade to the patched release most closely related to your
current version of BIND. These can all be downloaded from
- BIND 9 version 9.9.9-P8
- BIND 9 version 9.10.4-P8
- BIND 9 version 9.11.0-P5
BIND Supported Preview Edition is a special feature preview
branch of BIND provided to eligible ISC support customers.
- BIND 9 version 9.9.9-S10
New development releases of BIND are also available which
contain the fix for this vulnerability.
- BIND 9 version 9.9.10rc3
- BIND 9 version 9.10.5rc3
- BIND 9 version 9.11.1rc3
ISC would like to thank Mike Lalumiere of Dyn, Inc., for bringing
this issue to our attention.
Document Revision History:
1.0 Advance Notification 20 March 2017
1.1 Revised Acknowledgements and Versions Affected 22 March 2017
1.2 Added mention of maintenance releases to the Solution section
31 March 2017
2.0 Public Announcement 12 April 2017
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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Advance Security Notifications, please visit http://www.isc.org/support/.
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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 here: https://kb.isc.org/article/AA-00861
This Knowledge Base article https://kb.isc.org/article/AA-01471 is
the complete and official security advisory document.
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