A new, unpatched vulnerability exists in one of Microsoft's server products, the company warned late Monday.

In a technical bulletin, the company said it is looking into "public reports of a possible vulnerability in Microsoft Internet Information Services (IIS)."

The company said that a flaw exists in a certain type of Web serving operation.

"An elevation of privilege vulnerability exists in the way that the WebDAV extension for IIS handles HTTP requests," Microsoft said. "An attacker ...