Microsoft Visual Basic ActiveX Remote Code Execution Vulnerability

Notification Type: IBM Internet Security Systems Protection Advisory
Notification Date: June 09, 2009
Notification Version: 1.1
Name: Microsoft Visual Basic ActiveX Remote Code Execution Vulnerability
Public disclosure/
In the wild date:
June 09, 2009


Description: MSCOMM32.OCX ATL Loader, a prevalent Microsoft ActiveX control related to Microsoft Visual Basic, is vulnerable to a buffer overflow that could result in remote code execution.
Discoverer: Robert Freeman of the IBM X-Force


ISS Coverage

Product Content Version
Network Sensor 7.0
Proventia A
Proventia IPS (G/GX)
Server Sensor 7.0
Proventia Multifunction Appliance
Proventia Server (Linux)
Proventia Server (Windows)
Proventia Desktop
Propagation Techniques ISS Protection Available
remote exploit


Nov 11, 2008

Detailed Description

Business Impact:

Plug-ins, like this ActiveX control, are one of the top targets of malicious web exploit toolkit developers.  These web exploit toolkits now account for nearly all browser-related exploits seen in the wild.  The exploitation of this ActiveX control provides the attacker with the privileges of the end user, which could allow complete control over the targeted endpoint.

Although this ActiveX control is not installed by default, most PCs have it.  Nearly all Visual Basic applications include this DLL during the installation process, and, since it's considered a shared component of these applications, it is typically left on the system even after an uninstall.  So, if a Visual Basic program has ever been installed on a computer, it probably has this ActiveX control installed, too, which makes this component highly prevalent, and, therefore, a lucrative target for attackers.

CVSS: Base Score: 9.3
  Access Vector: Network
Access Complexity: Medium
Authentication: None
Confidentiality Impact: Complete
Integrity Impact: Complete
Availability Impact: Complete
Adjusted Temporal Score: 6.9
  Exploitability: High
Remediation Level: Official Fix
Report Confidence: Confirmed
Affected Products: For a full list of affected versions, see references below.
Technical Description:

The Microsoft ATL is a collection of C++ template code that enables rapid development of programs through the use of prebuilt code.  MSCOMM32 uses a custom version of the ATL which is remotely exploitable. Although part of the Visual Basic 6 runtime and not a default component of the Windows OS, the MSCOMM32 ActiveX control is ubiquitous. The vulnerability regards loading persisted data through the ATL abstraction layer into COM controls this library exports; the result is that a heap overflow may occur. X-Force has confirmed that reliable remote code execution is possible.


Patches are available for this issue. See References for details.



Revision History

1.0 Initial publication.
1.1 Listed Robert Freeman as the discoverer.

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