Modifications to ACLs (Access Control Lists) in Microsoft Exchange 5.5 do not take effect until the directory store cache is refreshed.
Microsoft Exchange Server 5.5 and 5.0 does not properly handle (1) malformed NNTP data, or (2) malformed SMTP data, which allows remote attackers to cause a denial of service (application error).
Microsoft Outlook and Outlook Express allow remote attackers to cause a denial of service by sending email messages with blank fields such as BCC, Reply-To, Return-Path, or From.
The installation of Microsoft Exchange 2000 before Rev. A creates a user account with a known password, which could allow attackers to gain privileges, aka the “Exchange User Account” vulnerability.
Buffer overflow in Internet Mail Service (IMS) for Microsoft Exchange 5.5 and 5.0 allows remote attackers to conduct a denial of service via AUTH or AUTHINFO commands.
IIS 5.0 and Microsoft Exchange 2000 allow remote attackers to cause a denial of service (memory allocation error) by repeatedly sending a series of specially formatted URL’s.