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IBM AIX TCP Large Send Offload Bug Lets Remote Users Deny Service
SecurityTracker Alert ID: 1026640|
SecurityTracker URL: http://securitytracker.com/id/1026640
(Links to External Site)
Date: Feb 4 2012
Denial of service via network|
Fix Available: Yes Vendor Confirmed: Yes |
Version(s): 5.3, 6.1, 7.1|
A vulnerability was reported in IBM AIX. A remote user can cause denial of service conditions.|
A remote user can send a series of specially crafted TCP packets to trigger a kernel panic on the target system.
Systems with the TCP large send offload option enabled on a network interface are affected.
A remote user can cause the target system to crash.|
The vendor has issued a fix (APARs IV13827, IV13751, IV13820, IV14209, IV14210, IV14211).|
The vendor's advisory is available at:
Vendor URL: aix.software.ibm.com/aix/efixes/security/large_send_advisory.asc (Links to External Site)
Source Message Contents
Date: Sat, 04 Feb 2012 18:07:22 +0000|
Subject: IBM AIX
-----BEGIN PGP SIGNED MESSAGE-----
IBM SECURITY ADVISORY
First Issued: Fri Feb 3 10:20:44 CST 2012
The most recent version of this document is available here:
VULNERABILITY: Vulnerability in AIX TCP stack
PLATFORMS: AIX 5.3, 6.1, and 7.1 releases
SOLUTION: Apply the fix as described below.
THREAT: TCP network packet denial of service
CVE Number: CVE-2012-0194
Reboot required? YES
Protected by FPM? NO
Protected by SED? NO
AIX could allow a remote attacker to cause a denial of service, caused
by an error when the TCP large send offload option is enabled on a
network interface. By sending a specially-crafted sequence of packets,
an attacker could exploit this vulnerability to cause a kernel panic.
CVSS Base Score: 7.1
CVSS Temporal Score: See http://xforce.iss.net/xforce/xfdb/72562 for the
CVSS Environmental Score*: Undefined
CVSS String: (AV:n/AC:m/Au:n/C:n/I:n/A:c)
III. PLATFORM VULNERABILITY ASSESSMENT
To determine if your system is vulnerable, execute the following
lslpp -L bos.net.tcp.client
The following fileset levels are vulnerable:
AIX Fileset Lower Level Upper Level
bos.net.tcp.client 188.8.131.52 184.108.40.206
bos.net.tcp.client 220.127.116.11 18.104.22.168
bos.net.tcp.client 22.214.171.124 126.96.36.199
bos.net.tcp.client 188.8.131.52 184.108.40.206
bos.net.tcp.client 220.127.116.11 18.104.22.168
bos.net.tcp.client 22.214.171.124 126.96.36.199
IBM has assigned the following APARs to this problem:
AIX Level APAR number Availability
5.3.12 IV13827 TBD sp6
6.1.5 IV13751 TBD sp9
6.1.6 IV13820 TBD sp8
6.1.7 IV14209 TBD sp4
7.1.0 IV14210 TBD sp5
7.1.1 IV14211 TBD sp4
Subscribe to the APARs here:
By subscribing, you will receive periodic email alerting you
to the status of the APAR, and a link to download the fix once
it becomes available.
Fixes are available. The fixes can be downloaded via ftp
The link above is to a tar file containing this signed
advisory, fix packages, and PGP signatures for each package.
The fixes below include prerequisite checking. This will
enforce the correct mapping between the fixes and AIX
AIX Level Interim Fix (*.Z)
To extract the fixes from the tar file:
tar xvf large_send_fix.tar
Verify you have retrieved the fixes intact:
The checksums below were generated using the
"csum -h SHA1" (sha1sum) command is the followng:
csum -h SHA1 (sha1sum) filename
To verify the sum, use the text of this advisory as input to sha1sum.
csum -h SHA1 -i Advisory.asc
sha1sum -c Advisory.asc
These sums should match exactly. The PGP signatures in the tar
file and on this advisory can also be used to verify the
integrity of the fixes. If the sums or signatures cannot be
confirmed, contact IBM AIX Security at
firstname.lastname@example.org and describe the discrepancy.
C. FIX AND INTERIM FIX INSTALLATION
IMPORTANT: If possible, it is recommended that a mksysb backup
of the system be created. Verify it is both bootable and
readable before proceeding.
To preview a fix installation:
installp -a -d fix_name -p all # where fix_name is the name of the
# fix package being previewed.
To install a fix package:
installp -a -d fix_name -X all # where fix_name is the name of the
# fix package being installed.
Interim fixes have had limited functional and regression
testing but not the full regression testing that takes place
for Service Packs; thus, IBM does not warrant the fully
correct functionality of an interim fix.
Interim fix management documentation can be found at:
To preview an interim fix installation:
emgr -e ipkg_name -p # where ipkg_name is the name of the
# interim fix package being previewed.
To install an interim fix package:
emgr -e ipkg_name -X # where ipkg_name is the name of the
# interim fix package being installed.
Adjust the lowest value from the common path MTUs table based on
Turn off large send function (may have performance impact)
Turn off path MTU discovery (may have performance impact)
VI. OBTAINING FIXES
AIX security fixes can be downloaded from:
AIX fixes can be downloaded from:
NOTE: Affected customers are urged to upgrade to the latest
applicable Technology Level and Service Pack.
VII. CONTACT INFORMATION
If you would like to receive AIX Security Advisories via email,
Comments regarding the content of this announcement can be
To request the PGP public key that can be used to communicate
securely with the AIX Security Team you can either:
A. Send an email with "get key" in the subject line to:
B. Download the key from a PGP Public Key Server. The key ID is:
Please contact your local IBM AIX support center for any
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.
Complete CVSS Guide: http://www.first.org/cvss/cvss-guide.html
On-line Calculator V2:
X-Force Vulnerability Database: http://xforce.iss.net/xforce/xfdb/72562
*The CVSS Environment Score is customer environment specific and will
ultimately impact the Overall CVSS Score. Customers can evaluate the
impact of this vulnerability in their environments by accessing the links
in the Reference section of this Flash.
Note: According to the Forum of Incident Response and Security Teams
(FIRST), the Common Vulnerability Scoring System (CVSS) is an "industry
open standard designed to convey vulnerability severity and help to
determine urgency and priority of response." IBM PROVIDES THE CVSS SCORES
"AS IS" WITHOUT WARRANTY OF ANY KIND, INCLUDING THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. CUSTOMERS ARE
RESPONSIBLE FOR ASSESSING THE IMPACT OF ANY ACTUAL OR POTENTIAL SECURITY
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.7 (AIX)
-----END PGP SIGNATURE-----
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