Microsoft Visual Studio 'Msmask32.ocx' ActiveX Control Remote Buffer Overflow Vulnerability



Date Discovered

August 13, 2008


The Microsoft Visual Studio ActiveX control, MaskedEdit, is prone to a stack-based buffer-overflow vulnerability because it fails to perform adequate boundary checks on user-supplied input. An attacker can exploit this issue to execute arbitrary code in the context of an application using the affected ActiveX control (typically Internet Explorer). Failed attacks will likely cause denial-of-service conditions. 'Msmask32.ocx' is vulnerable; other versions may also be affected. UPDATE: Testing indicates that 'Msmask32.ocx' is not vulnerable; we are working with Microsoft to confirm our findings and gain further details. We recommend that users install or a later version.

Technologies Affected

  • Microsoft Msmask32.ocx
  • Microsoft Visual FoxPro 8.0
  • Microsoft Visual FoxPro 8.0 SP1
  • Microsoft Visual FoxPro 9.0 SP1
  • Microsoft Visual FoxPro 9.0 SP2
  • Microsoft Visual Studio .NET 2002 SP1
  • Microsoft Visual Studio .NET 2003 SP1
  • Microsoft Visual Studio .NET 2002
  • Microsoft Visual Studio .NET 2003
  • Microsoft Visual Studio 6.0


Deploy network intrusion detection systems to monitor network traffic for malicious activity.
Deploy NIDS to monitor network traffic for signs of anomalous or suspicious activity. This includes but is not limited to requests that include NOP sleds and unexplained incoming and outgoing traffic. This may indicate exploit attempts or activity that results from a successful exploit.

Run all software as a nonprivileged user with minimal access rights.
To limit the potential damage that a successful exploit may achieve, run all nonadministrative software as a regular user with the least amount of privileges required to successfully operate.

Do not follow links provided by unknown or untrusted sources.
Do not follow links, visit websites, or open files that are provided by untrusted sources.

Set web browser security to disable the execution of script code or active content.
Since exploiting this issue allows malicious script code to run in web clients, consider disabling support for script code and active content within the client browser. Note that this mitigation tactic might adversely affect websites that rely on the execution of browser-based script code.

Implement multiple redundant layers of security.
Various memory-protection schemes (such as nonexecutable and randomly mapped memory segments) may hinder an attacker's ability to exploit this vulnerability to execute arbitrary code.

Microsoft has released an advisory and fixes to address this issue. Please see the references for more information.



Symantec's Security Intelligence Analysis Team

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