Software Engineering Institute

Microsoft Outlook contains a vulnerability in the way that it handles certain email message headers. According to Microsoft Security Bulletin MS07-003:

An attacker who successfully exploited the vulnerability could send a malformed e-mail to a user of Outlook that would cause the Outlook client to fail under certain circumstances. The Outlook client would continue to fail so long as the malformed e-mail message remained on the e-mail server. The e-mail message could be deleted by an e-mail administrator, or by the user via another e-mail client such as Outlook Web Access or Outlook Express, after which point the Outlook client would again function normally.

This vulnerability affects Microsoft Outlook 2000, Outlook 2002, and Outlook 2003.

A remote, unauthenticated attacker may be able to cause a denial of service.

Apply Update
Microsoft has issued an update to address this issue. See Microsoft Security Bulletin MS07-003. Note that Microsoft has documented known issues that occur after applying this update. See Microsoft Knowledgebase article 925938 for details.