Microsoft Visual Studio 'MSCOMM32.OCX' ActiveX Control Heap Buffer Overflow Vulnerability



Date Discovered

June 9, 2009


Microsoft Visual Studio is prone to a remote heap-based buffer-overflow vulnerability. Attackers may exploit this issue by enticing an unsuspecting victim to view a malicious webpage. Successful exploits will allow attackers to execute arbitrary code within the context of the affected application that uses the ActiveX control (typically Internet Explorer). Failed exploit attempts will result in a denial-of-service condition.

Technologies Affected

  • Microsoft Visual Basic 6.0 SP6


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.

Set web browser security to disable the execution of script code or active content.
Since attackers may use script code to exploit this issue, 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.

Do not use client software to access unknown or untrusted hosts from critical systems.
To limit exposure to client-side vulnerabilities, never visit sites of questionable integrity.

Do not accept communications that originate from unknown or untrusted sources.
Do not open or view email from unknown or untrusted sources. Configure email clients to view messages as plain text to help mitigate these issues.

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.

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.

The vendor has released an update. Please see the references for details.



Robert Freeman of ISS X-Force

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