============================================================================= ConnecTalk Inc. Security Advisory
Topic: Qpopper leaks information during authentication
Vendor: Eudora Product: qpopper 4.0.4 and qpopper 4.0.5 Note: other versions have not been tested. Problem found: May 14, 2003 Vendor notification: May 14, 2003 Second vendor notification: May 21, 2003 Public notification: June 18, 2003
Qpopper is the most widely-used server for the POP3 protocol (this allows users to access their mail using any POP3 client). Qpopper supports the latest standards, and includes a large number of optional features. Qpopper is normally used with standard UNIX mail transfer and delivery agents such as sendmail or smail.
II. Problem Description
When Qpopper is in the authentication phase, using plain text passwords, the response to the PASS command differs depending on the existance of the USER. If a valid username and a wrong password are given, Qpopper returns a negative reponse and waits for one more command before closing the connection. If an invalid username and password are given, Qpopper returns a negative response and disconnects right away.
A remote attacker can use this information leak to validate the existance of a user account.
-- Marc Lafortune firstname.lastname@example.org Intégrateur / Integrator ConnecTalk Inc. http://www.connectalk.com