Security Advisory: CVE-2011-2465 ISC BIND 9 Remote Crash with Certain RPZ Configurations

Barry Greene <bgreene@xxxxxxx> · Tue, 5 Jul 2011 06:54:44 -0700

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ISC BIND 9 Remote Crash with Certain RPZ Configurations

Two defects were discovered in ISC's BIND 9 code. These defects only affect
BIND 9 servers which have recursion enabled and which use a specific
feature of the software known as Response Policy Zones (RPZ) and where the
RPZ zone contains a specific rule/action pattern.

CVE: CVE-2011-2465

Document Version:  2.0

Posting date: 05 Jul 2011

Program Impacted: BIND

Versions affected:  9.8.0, 9.8.0-P1, 9.8.0-P2 and 9.8.1b1 Other versions of
BIND 9 not listed here are not vulnerable to this problem.

Severity:  High

Exploitable:  Remotely

Description: 

A defect in the affected versions of BIND could cause the "named" process
to exit when queried, if the server has recursion enabled and was
configured with an RPZ zone containing certain types of records.
Specifically, these are any DNAME record and certain kinds of CNAME
records.

The patch release of BIND 9.8.0-P4 alters the behavior of RPZ zones by
ignoring any DNAME records in an RPZ zone, and correctly returning CNAME
records from RPZ zones.

Note that DNAME has no defined effect on the RPZ engine and its presence in
an RPZ zone is ignored. The definitive list of meaningful patterns in an
RPZ zone is given in the BIND 9 Administrative Reference Manual and also in
ISC Technical Note 2010-1.

CVSS Score: 7.8

CVSS Equation: (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

Workarounds: 

Do not put certain CNAME or any DNAME records into an RPZ zone file until
your software can be patched. If you subscribe to a service which supplies
your RPZ zone data, ensure that it does not contain any DNAME or certain
CNAME records. The CNAME records which must not be used are those which
signal the RPZ engine to rewrite query names. CNAME records which signal
the RPZ engine to forge an NXDOMAIN response are not affected by this
defect.

An example of an RPZ rule which causes a query name to be rewritten is:

*.malicious-domain.com CNAME walled-garden.isp.net

An example of an RPZ rule which causes an NXDOMAIN response to be returned
is:

*.malicious-domain.com CNAME .

Please refer to the BIND 9 Administrative Reference Manual or to ISC
Technical Note 2010-1 for more information about the Response Policy Zone
(RPZ) feature which was added to BIND 9 in Version 9.8.0.

Active exploits: 

ISC received reports of this software flaw and verified the report's
accuracy.

Solution: 

Upgrade to: 9.8.0-P4. (Note that 9.8.0-P3 is not affected but has been
replaced by 9.8.0-P4 due to CVE-2011-2464)

Download this version from the following location:

ISC releases of BIND 9 software may be downloaded from
http://www.isc.org/software/bind

If you do not obtain your BIND software directly from ISC, contact your
operating system or software vendor for an update.

If you are participating in ISC's Beta or release candidate (RC) program,
please upgrade. ISC Beta/RC testers are expected to remove vulnerable
versions and upgrade. No security advisories are issued for beta / release
candidates once the corresponding final release is made.

Acknowledgement: ISC thanks Bryce Moore from TELUS Security Labs for
finding and reporting this issue.

Document Revision History

Version 1.0 - 14 June 2011: Phase One Disclosure Date
Version 1.1 - 20 June 2011: Phase Two Disclosure Date with updates.
Version 1.2 - 21 June 2011: Updates on beta, RC, and clarity editing
Version 1.3 - 24 June 2011: Added document URL
Version 1.4 - 28 June 2011:  Updated Solution and description (revised to
recommend 9.8.0-P4 per CVE-2011-2464)
Version 1.5 - 4 July 2011:  Phase Three and Four Disclosure Date
Version 2.0 - 5 July 2011:  Public Disclosure

References:

Do you have Questions? Questions regarding this advisory should go to
security-officer@xxxxxxx.

Do you need Software Support? Questions on ISC's Support services or other
offerings should be sent to sales@xxxxxxx. More information on 

ISC's support and other offerings are available at:
http://www.isc.org/community/blog/201102/BIND-support

ISC Security Vulnerability Disclosure Policy Details of our current
security advisory policy and practice can be found here:
https://www.isc.org/security-vulnerability-disclosure-policy

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