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             AUSCERT External Security Bulletin Redistribution

                               ESB-2010.0343
          Vulnerability in VBScript Scripting Engine Could Allow
                           Remote Code Execution
                               14 April 2010

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        AusCERT Security Bulletin Summary
        ---------------------------------

Product:           VBScript Scripting Engine
Publisher:         Microsoft
Operating System:  Windows Server 2003
                   Windows XP
                   Windows 2000
Impact/Access:     Execute Arbitrary Code/Commands -- Remote with User Interaction
Resolution:        Patch/Upgrade
CVE Names:         CVE-2010-0483  

Reference:         ESB-2010.0210

Original Bulletin: 
   http://www.microsoft.com/technet/security/bulletin/ms10-022.mspx

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Microsoft Security Bulletin (981169)

Vulnerability in VBScript Scripting Engine Could Allow Remote Code Execution

Published: April 13, 2010

Version: 1.0

General Information

Executive Summary

  This security update resolves a publicly disclosed vulnerability in VBScript
  on Microsoft Windows that could allow remote code execution. This security
  update is rated Important for Microsoft Windows 2000, Windows XP, and Windows
  Server 2003. On Windows Server 2008, Windows Vista, Windows 7, and Windows
  Server 2008 R2, the vulnerable code is not exploitable, however, as the code
  is present, this update is provided as a defense-in-depth measure and has no
  severity rating.

  The vulnerability could allow remote code execution if a malicious Web site
  displayed a specially crafted dialog box on a Web page and a user pressed the
  F1 key, causing the Windows Help System to be started with a Windows Help File
  provided by the attacker. If a user is logged on with administrative user
  rights, an attacker who successfully exploited this vulnerability could take
  complete control of an affected system.

  The security update addresses the vulnerability by modifying the way that the
  VBScript engine processes help files in protected mode.

  This security update addresses the vulnerability first described in Microsoft
  Security Advisory 981169.

  Recommendation: The majority of customers have automatic updating enabled and
  will not need to take any action because this security update will be
  downloaded and installed automatically. Customers who have not enabled
  automatic updating need to check for updates and install this update manually.

  For information about specific configuration options in automatic updating,
  see Microsoft Knowledge Base Article 294871.

  For administrators and enterprise installations, or end users who want to
  install this security update manually, Microsoft recommends that customers
  apply the update at the earliest opportunity using update management software,
  or by checking for updates using the Microsoft Update service.

Affected Software

  Microsoft Windows 2000 Service Pack 4
  Windows XP Service Pack 2
  Windows XP Service Pack 3
  Windows XP Professional x64 Edition Service Pack 2
  Windows Server 2003 Service Pack 2
  Windows Server 2003 x64 Edition Service Pack 2
  Windows Server 2003 with SP2 for Itanium-based Systems

Mitigating Factors

  This vulnerability cannot be exploited on Windows Vista, Windows Server 2008,
  Windows 7, or Windows Server 2008 R2.

  This vulnerability requires user interaction. The vulnerability could not be
  exploited without user interaction even if the user visited a malicious Web
  site. Instead, an attacker would need to persuade a user to press the F1 key
  on the keyboard while the Web site displays a scripted dialog box.

  In a Web-based attack scenario, an attacker could host a Web site that
  contains a Web page that is used to exploit this vulnerability. In addition,
  compromised Web sites and Web sites that accept or host user-provided content
  or advertisements could contain specially crafted content that could exploit
  this vulnerability. In all cases, however, an attacker would have no way to
  force users to visit these Web sites. Instead, an attacker would have to
  convince users to visit the Web site, typically by getting them to click a
  link in an e-mail message or Instant Messenger message that takes users to the
  attackers Web site.

  By default, all supported versions of Microsoft Outlook, Microsoft Outlook
  Express, and Windows Mail open HTML e-mail messages in the Restricted sites
  zone, removing the risk of an attacker being able to use this vulnerability to
  execute malicious code. The Restricted sites zone helps mitigate attacks that
  could try to exploit this vulnerability by preventing Active Scripting and
  ActiveX controls from being used when reading HTML e-mail messages. However,
  if a user clicks a link in an e-mail message, the user could still be
  vulnerable to exploitation of this vulnerability through the Web-based attack
  scenario. Additionally, Outlook 2007 uses a different component to render HTML
  e-mail, removing the risk of this exploit.

  By default, Internet Explorer on Windows Server 2003 runs in a restricted mode
  that is known as Enhanced Security Configuration. This mode sets the security
  level for the Internet zone to High. This is a mitigating factor for Web sites
  that you have not added to the Internet Explorer Trusted sites zone.

  An attacker who successfully exploited this vulnerability could gain the same
  user rights as the local user. Users whose accounts are configured to have
  fewer user rights on the system could be less affected than users who operate
  with administrative user rights.

Workarounds

Do not press the F1 key when prompted by a Web site

  Successful exploitation of this vulnerability requires that users assist the
  exploit by pressing the F1 key on their keyboard. Our analysis shows that if
  users do not press the F1 key on their keyboard, the vulnerability cannot be
  exploited.

  Consequently, malicious Web sites may attempt to convince users to press the
  F1 key. Such a Web site could invoke an endless loop of dialog boxes that tell
  the user to press the F1 key to end the loop, or offer information such as
  pricing information or help to be revealed through the F1 key.

  Users are advised to avoid pressing F1 presented by Web pages or other
  Internet content. If a dialog box appears repeatedly in an attempt to convince
  the user to press F1, users may log off the system or use Task Manager to
  terminate the Internet Explorer process.

Restrict access to the Windows Help System

  Successful exploitation of this vulnerability requires that the Windows Help
  System is functioning. You can help protect against exploitation of this
  vulnerability if you modify the ACL on winhlp32.exe to be more restrictive on
  Windows 2000, Windows XP, and Windows Server 2003 by running the following
  command from an administrative command line:

    echo Y | cacls "%windir%\winhlp32.exe" /E /P everyone:N

  Note You must be logged in as administrator or have administrative credentials
  to complete this workaround.

Set Internet and Local intranet security zone settings to "High" to block
ActiveX Controls and Active Scripting in these zones

  You can help protect against exploitation of this vulnerability by changing
  your settings for the Internet security zone to block ActiveX controls and
  Active Scripting. You can do this by setting your browser security to High.

Vulnerability Information

VBScript Help Keypress Vulnerability - CVE-2010-0483

  A remote code execution vulnerability exists in the way that VBScript
  interacts with Windows Help files when using Internet Explorer. If a malicious
  Web site displayed a specially crafted dialog box and a user pressed the F1
  key, the Windows Help System would be started with a Windows Help File
  provided by the attacker. If a user is logged on with administrative user
  rights, an attacker who successfully exploited this vulnerability could take
  complete control of an affected system. An attacker could then install
  programs; view, change, or delete data; or create new accounts with full user
  rights. Users whose accounts are configured to have fewer user rights on the
  system could be less impacted than users who operate with administrative user
  rights. On systems running Windows Server 2003, Internet Explorer Enhanced
  Security Configuration is enabled by default, which helps to mitigate against
  this issue.

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