Microsoft Visual Basic for Applications contains a vulnerability that could allow an unauthenticated, remote attacker to execute arbitrary code. Updates are available.
Description
Microsoft Visual Basic for Applications (VBA) contains a vulnerability that could allow an unauthenticated, remote attacker to execute arbitrary code.
The vulnerability is due to errors in processing documents that contain ActiveX controls. An unauthenticated, remote attacker could exploit this vulnerability by convincing a user to view a malicious document. A successful exploit could allow the attacker to execute arbitrary code with the privileges of the user.
Microsoft has confirmed this vulnerability in a security bulletin and released software updates to correct it.
Warning Indicators
Microsoft Visual Basic for Applications is vulnerable. Any applications with the VBA runtime are also vulnerable, including the following Microsoft Office products:
Microsoft Office XP SP3 and prior
Microsoft Office 2003 SP3 and prior
Microsoft Office 2007 SP2 and prior
IntelliShield Analysis
To exploit the vulnerability, an attacker must convince a user to view a malicious Microsoft Office document. The attacker may provide documents to users as attachments to e-mail messages or posted on public websites. The attacker may also use social engineering techniques in an attempt to convince users to open a provided document.
Systems that restrict user privileges are at less risk in the event of an exploit because any code execution would occur in a limited security context. However, an exploit against a system on which a user runs applications with Administrator privileges could result in a complete system compromise because the attacker could run arbitrary code to install malicious software or create new user accounts with elevated privileges.
The Cisco Applied Intelligence team has created an Applied Mitigation Bulletin to address vulnerabilities that Microsoft disclosed in the May 2010 security bulletin release. This Cisco bulletin, which assists administrators in identifying or mitigating these vulnerabilities using Cisco devices, is available at the following link: Cisco Applied Mitigation Bulletin: Microsoft Security Bulletin Release for May 2010.
Vendor Announcements
Microsoft has released a security bulletin at the following link: MS10-031
Impact
An unauthenticated, remote attacker could exploit this vulnerability to execute arbitrary code with the privileges of the user. If the user holds elevated privileges, the attacker could execute arbitrary code to gain complete control of the system.
Technical Information
The vulnerability is due to errors in processing documents that contain ActiveX controls. Memory corruption may occur in the memory stack when VBA searches for ActiveX controls in a Microsoft Office document. An unauthenticated, remote attacker could exploit the vulnerability by convincing a user to view a malicious document. When viewed, the document could cause memory corruption that the attacker could use to execute arbitrary code with the privileges of the user.
Safeguards
Administrators are advised to apply the available software updates.
Administrators may consider restricting access to the vbe6.dll library to prevent embedded ActiveX controls from running in Microsoft Office.
Users may consider applying the Microsoft Office Isolated Conversion Environment (MOICE) to safely open Word, Excel, and PowerPoint files from suspicious or unrecognized sources on systems that are running Microsoft Office 2003 or Office 2007.
Users are advised not to open e-mail messages from suspicious or unrecognized sources. If users cannot verify that links or attachments included in e-mail messages are safe, they are advised not to open them.
Users are advised to run applications with the least necessary privileges.
Administrators are advised to monitor critical systems.
Patches/Software
Microsoft customers can obtain updates directly by using the links in the security bulletin. These updates are also distributed by Windows automatic update features and available on the Windows Update website. Microsoft Windows Server Update Services (WSUS), Systems Management Server, and System Center Configuration Manager can assist administrators in deploying software updates.
Signatures
Cisco Systems Cisco Intrusion Prevention System (IPS) 6.0
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