Public Vulnerability Reports

Multiple Vendor Insecure Call to CreateProcess() Vulnerability

11.15.05

BACKGROUND

The Microsoft Windows API includes the CreateProcess() function as a
means to create a new process and it's primary thread.
CreateProcessAsUser() is similar but allows for the process to be run in
the security context of a particular user.

DESCRIPTION

The format of the CreateProcess() function is as follows:

BOOL CreateProcess(
  LPCTSTR lpApplicationName,
  LPTSTR lpCommandLine,
  LPSECURITY_ATTRIBUTES lpProcessAttributes,
  LPSECURITY_ATTRIBUTES lpThreadAttributes,
  BOOL bInheritHandles,
  DWORD dwCreationFlags,
  LPVOID lpEnvironment,
  LPCTSTR lpCurrentDirectory,
  LPSTARTUPINFO lpStartupInfo,
  LPPROCESS_INFORMATION lpProcessInformation
);

The 'lpApplicationName' variable contains the name of the module to be
executed. However, this can be a NULL value, in which case, the module
name to be executed will be the first white space-delimited token in the
lpCommandLine string.

It is a known issue, that if lpApplicationName contains a NULL value and
the full module path in the lpCommandLine variable contains white space
and is not enclosed in quotation marks, it is possible that an alternate
application will be executed. Consider the following scenario:

   CreateProcess(
      NULL,
      c:program filessub dirprogram.exe,
      ...
   );

In this case, the system will successively expand the string when
interpreting the file path, until a module is encountered to execute.
The string used in the above example would be interpreted as follows:

   c:program.exe filessub dirprogram name
   c:program filessub.exe dirprogram name
   c:program filessub dirprogram.exe

Therefore, if a file named program.exe existed in the c: directory, it
would be executed instead of the intended application. This is a known
issue, discussed directly in the API documentation:

http://msdn.microsoft.com/library/en-us/dllproc/base/createprocessasuser.asp

ANALYSIS

Despite the fact that this is a known issue, several popular
applications, insecurely call the CreateProcess() and
CreateProcessAsUser() functions. This creates a scenario whereby
arbitrary code could be executed. In the scenario detailed above, if an
attacker were able to install arbitrary code in a file at
c:program.exe, when the vulnerable application was launched, the code
would be executed. The arbitrary code would generally be executed under
the privileges of the executing user but could also be launched with
elevated privileges if an insecure call were made CreateProcessAsUser()
using elevated privileges. This attack would involve some form of social
engineering or need to be combined with another attack to first get the
arbitrary code installed in the correct location.

DETECTION

The following applications have been confirmed to be vulnerable:

Vendor:     RealNetworks
Application: RealPlayer 10.5
Files:     realplay.exe
        realjbox.exe
       
Vendor:     Kaspersky
Application: Kaspersky Anti-Virus for Windows File Servers 5.0 (English) - Installation File
Files:     kav5.0trial_winfsen.exe

Vendor:     Apple
Application: iTunes 4.7.1.30
Files: iTunesHelper.exe

Vendor:     VMWare
Application: VMWare Workstation 5.0.0 build-13124
Files:     VMwareTray.exe
        VMwareUser.exe
       
Vendor:     Microsoft
Application: Microsoft Antispyware 1.0.509 (Beta 1)
Files:     GIANTAntiSpywareMain.exe
        gcASNotice.exe
        gcasServ.exe
        gcasSWUpdater.exe
        GIANTAntiSpywareUpdater.exe

Note: The vulnerability in Microsoft Antispyware was previously
discussed on the Full-Disclosure mailing list
(http://lists.grok.org.uk/pipermail/full-disclosure/2005-May/033909.html)
but remains unpatched.

WORKAROUND

Ensure that unexpected files are not stored in locations that can be
used for this attack. Windows XP SP2 will alert a user of the existence
of a file named c:program.exe when it first boots, however, any path
containing white space where a vulnerable application is stored could be
used in this attack.

VENDOR RESPONSE

The following vendor responses have been provided.

Apple:

"Due to the way iTunes 5 launches its helper application, multiple
system paths are searched for which program to run. This may allow a
malicious user on the local system to create an environment where an
alternate program will be executed by iTunes. iTunes 6 addresses this
issue and can be obtained from http://www.apple.com/itunes/download/.
Credit to iDEFENSE for reporting this issue to us."

Kaspersky:

"We are currently looking into the problem, and it seems that this is
not present in the current version of KAV for File Servers."

Microsoft:

"Microsoft has confirmed that the Beta 2 version of its Antispyware
product, targeted for release later this year, will address the issue
reported by iDEFENSE."

CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
following names to this issue.

RealNetworks RealPlayer 10.5
  CAN-2005-2936

Kaspersky Anti-Virus 5.0
  CAN-2005-2937

Apple iTunes 4.7.1.30
  CAN-2005-2938

VMWare Workstation 5.0.0 build-13124
  CAN-2005-2939

Microsoft Antispyware 1.0.509 (Beta 1)
  CAN-2005-2940

Theses are candidates for inclusion in the CVE list
(http://cve.mitre.org), which standardizes names for security problems.

DISCLOSURE TIMELINE

09/19/2005   Initial vendor notification
11/15/2005   Coordinated public disclosure

CREDIT

The discoverer of this vulnerability wishes to remain anonymous.

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LEGAL NOTICES

Copyright © 2005 Verisign, Inc.

Permission is granted for the redistribution of this alert
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Disclaimer: The information in the advisory is believed to be accurate
at the time of publishing based on currently available information. Use
of the information constitutes acceptance for use in an AS IS condition.
There are no warranties with regard to this information. Neither the
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