[VulnWatch] Microsoft Virtual PC Services Insecure Temporary File Creation

From: Advisories (advisories_at_atstake.com)
Date: 02/10/04

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                                    @stake, Inc.
                                  www.atstake.com
                                 Security Advisory
    Advisory Name: Virtual PC Services Insecure Temporary File Creation
     Release Date: 02/10/2004
      Application: Connectix Virtual PC 6.0.x
                   Microsoft Virtual PC 6.1
         Platform: Mac OS X
         Severity: Local privilege escalation
           Author: George Gal <ggal@atstake.com>
    Vendor Status: Vendor has updated version of the software
    CVE Candidate: CAN-2004-0115
        Reference: www.atstake.com/research/advisories/2004/a021004-1.txt

    Overview:
    Virtual PC is a popular x86 virtual machine emulator capable running
    several guest operating systems under the Mac OS X and Windows
    platforms. Virtual PC provides a set of services for managing network
    sharing capabilities under Mac OS X. These services are spawned from
    the setuid root binary, VirtualPC_Services, which creats several
    temporary files when it is executed. The VirtualPC_Services does not
    check for several unsafe conditions prior to creation of these
    temporary files. As a result an attacker with interactive login
    access to the system may leverage insecure temporary files to become
    root or overwrite critical system files.

    Details:
    @stake has identified a vulnerability within the setuid root binary,
    VirtualPC_Services, due to its inability to check for dangerous
    conditions prior to temporary file creation. This vulnerability
    allows an attacker to truncate and overwrite arbitrary files in
    addition to creation of arbitrary files with insecure file
    permissions.
    Using this vulnerability it is feasible for an attacker to gain root
    privileges on the system. The VirtualPC_Services binary creates a
    log file upon startup as /tmp/VPCServices_Log. An attacker may
    create a symbolic link in the /tmp/ directory as VPCServices_Log
    pointing to an arbitrary file to be overwritten when the
    VirtualPC_Services binary is executed. However, when the symbolic
    link points to a non-existent file a new file is created with file
    permissions determined by the unprivileged user's umask(2) settings.

    Vendor Response:
    Microsoft has an updated version of the software available.
    Download information available at:
    http://www.microsoft.com/technet/security/bulletin/MS04-005.asp

    Recommendation:
    If possible install the updated version of Virtual PC.
    Do not install Virtual PC on a multi-user machine. If this is a
    requirement, only allow users with in a particular group to access
    Virtual PC.

    Common Vulnerabilities and Exposures (CVE) Information:
    The Common Vulnerabilities and Exposures (CVE) project has assigned
    the following names to these issues. These are candidates for
    inclusion in the CVE list (http://cve.mitre.org), which standardizes
    names for security problems.

       CAN-2004-0115
    @stake Vulnerability Reporting Policy:
    http://www.atstake.com/research/policy/
    @stake Advisory Archive:
    http://www.atstake.com/research/advisories/
    PGP Key:
    http://www.atstake.com/research/pgp_key.asc
    Copyright 2004 @stake, Inc. All rights reserved.

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