Lotus Notes R5 S/MIME Vulnerability
Lotus Notes R5 Client enables users to combine e-mail, calendaring, group scheduling, contact and task management, Web browsing, and knowledge management into a single application. Lotus Notes supports the S/MIME standard which is a secure method of sending and receiving email, allowing messages to be encrypted and sending digital certificates as part of the message.
Due to the implementation of the S/MIME standard with Lotus Notes R5 Client, a user receiving email is not notified if the mail has been tampered with.
Upon receiving a mail message with a broken signature the message will appear to be an unsigned email. Lotus Notes will not notify a user if the mail has been modified by a third party. When receiving a corrupted encrypted email, the mail message will appear to be blank. Again Lotus Notes will not inform a user of corruption.
Since Lotus Notes does not tell the user about corrupted signed messages, this vulnerability may allow attackers to corrupt signed messages in transit and not have them noticed by the recipient (though they will be listed as unsigned).