Eudora before 6.1.1 allows remote attackers to cause a denial of service (crash) via an e-mail with a long "To:" field, possibly due to a buffer overflow.
Eudora 5.0.2 allows a remote attacker to read arbitrary files via an email with the path of the target file in the "Attachment Converted" MIME header, which sends the file when the email is forwarded to the attacker by the user.
Eudora before 5.1 allows a remote attacker to execute arbitrary code, when the 'Use Microsoft Viewer' and 'allow executables in HTML content' options are enabled, via an HTML email message containing Javascript, with ActiveX controls and malicious code within IMG tags.