It didn't take long to surface but Microsoft has revealed that it is is investigating a potential security issue with Exchange Server 2003. This is the first known bug since the e-mail server was launched last month.

The potential flaw lies in the Outlook Web Access (OWA) component of Exchange Server 2003. A network administrator at a Nashville, Tennessee, provider of investment performance reporting tools found that users logging in to OWA could be logged in to another user's mailbox at random and have full access privileges.

"This seems to be a major security flaw and we have had to shut off OWA indefinitely because of the issue," the network administrator wrote in a posting to NTBugtraq, a well-known security mailing list.

A preliminary investigation by Microsoft indicated that the issue occurs only with Kerberos authentication disabled, which the vendor said is uncommon. "We recommend that our customers ensure that Kerberos authentication is enabled, which is the default configuration," Microsoft said in a statement Friday.

Microsoft has already developed a patch, which is currently being tested, the network administrator said in an e-mail message. Microsoft would not comment on any patch because it is still investigating the issue.

"Upon completion of this investigation, Microsoft will take the appropriate action to protect our customers, including providing a fix and additional mitigation information if either is warranted," the vendor said.