Buffer overflow in various Microsoft applications for Macintosh allows remote attackers to cause a denial of service (crash) or execute arbitrary code by invoking the file:// directive with a large number of / characters which affects Internet Explorer 5.1 Outlook Express 5.0 through 5.0.2 Entourage v. X and 2001 PowerPoint v. X 2001 and 98 and Excel v. X and 2001 for Macintosh.