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AUSCERT External Security Bulletin Redistribution
ESB-2007.0634 -- [AIX]
New AIX APARs fix BIND remote DNS cache poisoning
22 August 2007
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AusCERT Security Bulletin Summary
---------------------------------
Product: Bind9
Operating System: AIX 5.3
AIX 5.2
Impact: Reduced Security
Provide Misleading Information
Access: Remote/Unauthenticated
CVE Names: CVE-2007-2926
Ref: AL-2007.0089
Original Bulletin: http://www.ibm.com/servers/eserver/support/unixservers/aixfixes.html
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IBM SECURITY ADVISORY
First Issued: Thu Aug 16 20:31:59 CDT 2007
===============================================================================
VULNERABILITY SUMMARY
VULNERABILITY: BIND remote DNS cache poisoning
PLATFORMS: AIX 5.2, 5.3
SOLUTION: Apply the APAR, interim fix or workaround as described
below.
THREAT: DNS cache may be poisoned due to week DNS query IDs.
CERT VU Number: CVE-2007-2926
CVE Number: 252735
===============================================================================
DETAILED INFORMATION
I. OVERVIEW
Berkeley Internet Name Domain 9 (BIND9) is a Domain Name System (DNS)
distribution from the Internet Systems Consortium (ISC) and it is included
with AIX 5.2 and 5.3. At this time, all versions of AIX 5.2 and 5.3 include
BIND 9.2.
II. DESCRIPTION
The ISC has issued a patch for a security vulnerability in some versions of
BIND 9 that can be exploited by a remote attacker to guess the DNS query
IDs and poison the DNS cache.
For more details please visit:
http://www.isc.org/sw/bind/bind-security.php
http://www.kb.cert.org/vuls/id/252735
III. IMPACT
From the ISC BIND advisory:
The DNS query id generation is vulnerable to cryptographic analysis
which provides a 1 in 8 chance of guessing the next query id for 50% of
the query ids. This can be used to perform cache poisoning by an
attacker.
This bug only affects outgoing queries, generated by BIND 9 to answer
questions as a resolver, or when it is looking up data for internal
uses, such as when sending NOTIFYs to slave name servers.
IV. PLATFORM VULNERABILITY ASSESSMENT
To determine if your system is vulnerable, run the following command:
# lslpp -l | grep bos.net.tcp.server
# lslpp -l | grep bos.net.tcp.client
The following filesets are vulnerable:
AIX Level Fileset Lower Level Upper Level
---------------------------------------------------------------
5.2.0 bos.net.tcp.server 5.2.0.85 5.2.0.107
5.2.0 bos.net.tcp.client 5.2.0.85 5.2.0.107
5.3.0 bos.net.tcp.server 5.3.0.40 5.3.0.62
5.3.0 bos.net.tcp.client 5.3.0.40 5.3.0.62
NOTE: The above filesets are those currently supported by IBM. Previous
versions of the fileset may also be vulnerable. Affected customers are
urged to upgrade to the latest applicable Technology Level and Service
Pack.
V. SOLUTIONS
A. APARS
IBM provides the following fixes:
AIX Level APAR number Availability
--------------------------------------------------------------------
5.2.0 IZ02218 10/31/2007 (subject to change)
5.3.0 IZ02219 11/27/2007 (subject to change)
AIX Version 5 APARs can be downloaded from:
http://www.ibm.com/servers/eserver/support/unixservers/aixfixes.html
NOTE: Affected customers are urged to upgrade to the latest applicable
Technology Level and Service Pack.
B. INTERIM FIXES
Interim fixes are available. The interim fix can be downloaded via
ftp from:
ftp://aix.software.ibm.com/aix/efixes/security/bindcrypt_ifix.tar.Z
This is a compressed tarball containing this advisory, interim fix
packages and PGP signatures for each package. The interim fixes below
include prerequisite checking. This will enforce the correct mapping
between the fixes and AIX Technology Levels.
AIX Release & Technology Level Interim fix
---------------------------------------------------------------
5200-08 IZ02218_08.070814.epkg.Z
5200-09 IZ02218_09.070814.epkg.Z
5200-10 IZ02218_10.070810.epkg.Z
5300-04 IZ02219_04.070814.epkg.Z
5300-05 IZ02219_05.070814.epkg.Z
5300-06 IZ02219_06.070810.epkg.Z
IMPORTANT: If possible, it is recommended that a mksysb backup of the
system be created. Verify it is both bootable and readable before
proceeding.
These interim fixes have not been fully regression tested; thus, IBM
does not warrant the fully correct functionality of the interim fix.
Customers install the interim fix and operate the modified version of
AIX at their own risk.
Verify you have retrieved the fixes intact:
The interim fixes below are named by using the technology level
corresponding to the release that the fix applies to. The checksums
below were generated using the "sum" and "md5sum" commands and are as
follows:
Filename sum md5sum
----------------------------------------------------------------------
IZ02218_08.070814.epkg.Z 40008 3296 5bf5384341dc7e00e0cc378e3144ae8b
IZ02218_09.070814.epkg.Z 26768 3291 e0e6ea57ff375715ed5cedd3238b8317
IZ02218_10.070810.epkg.Z 39720 3293 9528b87acaddfd83f7351eca2d946fb7
IZ02219_04.070814.epkg.Z 08276 3214 eb1326b75f19ac84eae237882044beb8
IZ02219_05.070814.epkg.Z 44939 3220 edaa7f8e167cbe3f5ca14040d648e1a9
IZ02219_06.070810.epkg.Z 29152 3228 886a25c351f61e2f1f1fa994bd780da3
These sums should match exactly. The PGP signatures in the
compressed tarball and on this advisory can also be used to verify
the integrity of the various files they correspond to. If the sums
or signatures cannot be confirmed, double check the command results
and the download site address. If those are OK, contact IBM AIX
Security at security-alert@austin.ibm.com and describe the
discrepancy.
C. INTERIM FIX INSTALLATION
These packages use the new Interim Fix Management Solution to install
and manage interim fixes. More information can be found at:
http://www14.software.ibm.com/webapp/set2/sas/f/aix.efixmgmt/home.html
To preview an epkg interim fix installation execute the following
command:
# emgr -e ipkg_name -p # where ipkg_name is the name of the
# interim fix package being previewed.
To install an epkg interim fix package, execute the following command:
# emgr -e ipkg_name -X # where ipkg_name is the name of the
# interim fix package being installed.
The "X" flag will expand any filesystems if required.
VI. WORKAROUNDS
If you are running BIND9 there are no known workarounds. If the service
is not needed and is running, shut it down.
VII. OBTAINING FIXES
AIX Version 5 APARs can be downloaded from:
http://www.ibm.com/servers/eserver/support/unixservers/aixfixes.html
Security related Interim Fixes can be downloaded from:
ftp://aix.software.ibm.com/aix/efixes/security
VII. CONTACT INFORMATION
If you would like to receive AIX Security Advisories via email, please
visit:
http://www14.software.ibm.com/webapp/set2/subscriptions/pqvcmjd
Comments regarding the content of this announcement can be directed to:
security-alert@austin.ibm.com
To request the PGP public key that can be used to communicate
securely with the AIX Security Team send email to
security-alert@austin.ibm.com with a subject of "get key". The key
can also be downloaded from a PGP Public Key Server. The key id is
0x4265D862.
Please contact your local IBM AIX support center for any assistance.
eServer is a trademark of International Business Machines Corporation.
IBM, AIX and pSeries are registered trademarks of International Business
Machines Corporation. All other trademarks are property of their
respective holders.
VIII. ACKNOWLEDGMENTS
This vulnerability was reported by ISC who credit Amit Klein from Trusteer
(http://www.trusteer.com/).
http://www.trusteer.com/docs/bind9dns.html
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