Although Microsoft has already released a workaround solution for the bug, it is still working on the permanent solution, it said.
In the meantime, it recommended those concerned use a protection system known as the Enhanced Mitigation Experience Toolkit.
The bug revolves around the way that IE manages a computer's memory when processing Cascading Style Sheets - a widely used technology that defines the look and feel of pages on a website.
Criminals can exploit IE's memory management to inject their own malicious code into the stream of instructions a computer processes as a browser is being used.
Installing and applying the toolkit may require Windows XP users to update the version of the operating system they are using. But even if they do that some of the protection it bestows on Windows 7 and Vista users will not be available.
We're currently unaware of any attacks trying to use the claimed vulnerability or of customer impact," the BBC quoted Dave Forstrom, the director of Microsoft's Trustworthy Computing group, as saying.
"As vulnerabilities go, this kind is the most serious as it allows remote execution of code. This means the attacker can run programs, such as malware, directly on the victim's computer," said Rik Ferguson, senior security analyst at Trend Micro.
He added, "It is highly reminiscent of a vulnerability at the same time two years ago which prompted several national governments to warn against using IE and to switch to an alternative browser."
