This indicates a possible attempt to exploit a heap overflow vulnerability in the Microsoft Windows GDI Graphics Rendering Engine.
An attacker can exploit this via malicious WMF (Windows Metafile) image that will cause a heap overflow when it is rendered by the engine. This can lead to the execution of arbitrary code.
Microsoft Windows ME
Microsoft Windows 98SE
Microsoft Windows 98
System compromise: remote code execution.
Microsoft has released critical update MS06-026. Please apply the patch to all vulnerable machines.
Users should never visit sites of questionable integrity or follow links provided by unfamiliar or untrusted sources.
Disable the execution of script code or active content in your web browser.
Disabling scripting and active content in the Internet Zone may limit exposure to this and other vulnerabilities.
Disabling client side support for HTML email may limit exposure to these types of attacks.