Topic: IBM AIX rm_mlcache_file Local Race Condition Vulnerability

Release Date: 2006-04-24

CVE CAN ID : CVE-2006-1247

Affected system:
==============
-IBM AIX 5.1
-IBM AIX 5.2
-IBM AIX 5.3

Unaffected system:
==============

Impact:
======
NSFocus Security Team discovered a local race condition in IBM AIX rm_mlcache_file which could allow a local user to overwrite arbitrary file.

Description:
==========
rm_mlcache_file shipped with IBM AIX is used to delete some cached files. By default it is set with suid root bit.

rm_mlcache_file contains a race condition when processing temporary files which allows a local attacker to overwrite arbitrary files. Attackers can launch attacks by running the program directly, or waiting till root user runs it.
Successful exploitation may result in data loss or DoS, specifically depending on the overwritten file.

Workaround:
===========
Remove the execution bit from rm_mlcache_file temporarily:

# chmod 000 /usr/bin/rm_mlcache_file

Vendor Status:
============
The vendor has released the following APAR patches to fix the vulnerability:

APAR number for AIX 5.1.0: IY82866
APAR number for AIX 5.2.0: IY82285
APAR number for AIX 5.3.0: IY82357

AIX 5 APAR patch can be downloaded at:
http://www.ibm.com/servers/eserver/support/unixservers/aixfixes.html

The temporary patch for the vulnerability can be downloaded at:
ftp://aix.software.ibm.com/aix/efixes/security/rm_mlcache_file_ifix.tar.Z

Additional Information:
==================
The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2006-1247 to this issue. This is a candidate for inclusion in the CVE list (http://cve.mitre.org), which standardizes names for security problems. Candidates may change significantly before they become official CVE entries.

Credit:
=====
Yang Jilong of NSFocus Security Team found the vulnerability.