qpopper 4.01 with PAM based authentication on Red Hat systems generates different error messages when an invalid username is provided instead of a valid name, which allows remote attackers to determine valid usernames on the system.
Vulnerabilities in Qualcomm Eudora WorldMail Server may allow remote attackers to cause a denial of service (crash) and possibly execute arbitrary code, as demonstrated by the PROTOS LDAPv3 test suite.
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.
Eudora 5.1 allows remote attackers to execute arbitrary code when the "Use Microsoft Viewer" option is enabled and the "allow executables in HTML content" option is disabled, via an HTML email with a form that is activated from an image that the attacker spoofs as a link, which causes the user to execute the form and access embedded attachments.
Eudora 4.x allows remote attackers to bypass the user warning for executable attachments such as .exe, .com, and .bat by using a .lnk file that refers to the attachment, aka "Stealth Attachment."
Qpopper 2.53 and 3.0 does not properly identify the \n string which identifies the end of message text, which allows a remote attacker to cause a denial of service or corrupt mailboxes via a message line that is 1023 characters long and ends in \n.