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IBM SECURITY ADVISORY

First Issued: Wed Aug 25 15:51:53 CDT 2010

The most recent version of this document is available here:

http://aix.software.ibm.com/aix/efixes/security/ftpd_advisory.asc

VULNERABILITY SUMMARY

VULNERABILITY: AIX ftpd buffer overflow vulnerability

PLATFORMS: AIX 5.3, and earlier releases

SOLUTION: Apply the fix or workaround as described below.

THREAT: A remote attacker may be able to execute arbirary
code on a vulnerable server.

CERT VU Number: n/a
CVE Number: n/a

Reboot required? NO
Workarounds? YES
Protected by FPM? NO
Protected by SED? NO

DETAILED INFORMATION

I. DESCRIPTION

There is a buffer overflow vulnerability in the ftp server. By
issuing an overly long NLST command, an attacker may cause a
buffer overflow.

The successful exploitation of this vulnerability allows a remote
attacker to get the DES encrypted user hashes off the server if
FTP is configured to allow write access using Anonymous account
or another account that is available to the attacker.

The following executable is vulnerable:

/usr/sbin/ftpd

Please see the following for more information:
http://www.exploit-db.com/exploits/14456/

II. PLATFORM VULNERABILITY ASSESSMENT

Note: To use the following commands on VIOS you must first
execute:

oem_setup_env

To determine if your system is vulnerable, execute the following
command:

lslpp -L bos.net.tcp.client

The following fileset levels are vulnerable:

AIX Fileset Lower Level Upper Level
------------------------------------------------
bos.net.tcp.client 5.3.9.0 5.3.9.9
bos.net.tcp.client 5.3.10.0 5.3.10.4
bos.net.tcp.client 5.3.11.0 5.3.11.4
bos.net.tcp.client 5.3.12.0 5.3.12.1

III. SOLUTION

A. FIXES

Fixes are now available. The fixes can be downloaded from:

http://aix.software.ibm.com/aix/efixes/security/ftpd_fix.tar

The links above are to a tar file containing this signed
advisory, fix packages, and PGP signatures for each package.

AIX Level VIOS Level Fix
------------------------------------------------------
5.3.9 IZ83252_09.100824.epkg.Z
5.3.10 IZ83274_10.100824.epkg.Z
5.3.11 IZ83275_11.100824.epkg.Z
5.3.12 IZ83276_12.100824.epkg.Z

To extract the fixes from the tar file:

tar xvf qoslist_fix.tar
cd qoslist_fix

Verify you have retrieved the fixes intact:

The checksums below were generated using the "csum -h SHA1"
(sha1sum) commands and are as follows:

csum -h SHA1 (sha1sum) filename
------------------------------------------------------------------
eebecb166c86462ce5ae150fa60a82dc08cfccda IZ83252_09.100824.epkg.Z
4598a4079cfe45b545c7d1d96dacbf4dda1b486e IZ83274_10.100824.epkg.Z
916fc41925d77c31478af8bd80e417d020fc6037 IZ83275_11.100824.epkg.Z
99117134e3cda009c6e19f5f334210e1a5ac4bab IZ83276_12.100824.epkg.Z

To verify the sums, use the text of this advisory as input to
csum or sha1sum. For example:

csum -h SHA1 -i ftpd_advisory.asc
sha1sum -c ftpd_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 and describe the
discrepancy at the following addresses:

security-alert@austin.ibm.com

B. 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.

Fix management documentation can be found at:

http://www14.software.ibm.com/webapp/set2/sas/f/aix.efixmgmt/home.html

To preview fix installation:

emgr -e fix_name -p # where fix_name is the name of the
# fix being previewed.

To install fix package:

emgr -e fix_name -X # where fix_name is the name of the
# fix being installed.

C. APARS

IBM has assigned the following APARs to this problem:

AIX Level APAR number Service pack date
--------------------------------------------------------
5.3.9 IZ83252 tbd
5.3.10 IZ83274 tbd
5.3.11 IZ83275 tbd
5.3.12 IZ83276 tbd

Subscribe to the APARs here:

http://www.ibm.com/support/docview.wss?uid=isg1IZ83252
http://www.ibm.com/support/docview.wss?uid=isg1IZ83274
http://www.ibm.com/support/docview.wss?uid=isg1IZ83275
http://www.ibm.com/support/docview.wss?uid=isg1IZ83276

By subscribing, you will receive periodic email alerting you
to the status of the APAR, and a link to download the service
pack when it becomes available.

IV. WORKAROUND

Configure ftp daemon to disallow write access to anonymous FTP
users will limit the ability to create a directory that can
trigger this vulnerability.

VI. CONTACT INFORMATION

If you would like to receive AIX Security Advisories via email,
please visit:

http://www.ibm.com/systems/support

and click on the "My notifications" link.

To view previously issued advisories, 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 obtain 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:

security-alert@austin.ibm.com

B. Download the key from our web page:

http://www.ibm.com/systems/resources/systems_p_os_aix_security_pgpkey.txt

C. Download the key from a PGP Public Key Server. The key ID is:

0x28BFAA12

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.

VII. ACKNOWLEDGMENTS

This vulnerability was publicly disclosed by Kingcope.

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