NSFOCUS Security Advisory (SA2006-03)

IBM AIX rm_mlcache_file Local Race Condition Vulnerability 

Release Date: 2006-04-24

CVE ID: CVE-2006-1247

http://www.nsfocus.com/english/homepage/research/0603.htm

Affected systems & software
===================
IBM AIX 5.1
IBM AIX 5.2
IBM AIX 5.3

Unaffected systems & software
===================

Summary
=========

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.

Acknowledgment
===============

Yang Jilong of NSFocus Security Team found the vulnerability.

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==========
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NSFOCUS Security Team <security@nsfocus.com>
NSFOCUS INFORMATION TECHNOLOGY CO.,LTD
(http://www.nsfocus.com)

PGP Key: http://www.nsfocus.com/homepage/research/pgpkey.asc
Key fingerprint = F8F2 F5D1 EF74 E08C 02FE 1B90 D7BF 7877 C6A6 F6DA