Microsoft is researching a possible vulnerability that a little-known Russian company claims resides in Microsoft Windows Service Pack 2, but says early analysis indicates there isn't a problem.

The Russian company, Positive Technologies, says it has found a way to bypass service-pack technologies known as data-execution protection and heap-overflow protection, which guard against certain types of worm and hacker attacks. Released in August, the service pack was designed to secure Windows XP.

According to its early analysis, "an attacker cannot use this method by itself to attempt to run malicious code on a user's system," Microsoft said in a statement.

Meanwhile, Microsoft plans to release several software patches on Tuesday. Security bulletins to be issued this week are for applications such as Microsoft SharePoint, .Net Framework, Microsoft Office, and Visual Studio, as well as Windows, Media Player, and MSN Messenger.