==================================================================== Alt-N MDaemon's WorldClient Username Enumeration Vulnerability ==================================================================== Software: Alt-N MDaemon v13.0.3 and prior versions Vendor: http://www.altn.com/ Vuln Type: Username Enumeration Remote: Yes Local: No Discovered by: QSecure and Demetris Papapetrou References: http://www.qsecure.com.cy/advisories/Alt-N_MDaemon_WorldClient_Username_Enumeration.html Discovered: 14/09/2012 Reported: 19/12/2012 Fixed: 15/01/2013 (http://files.altn.com/MDaemon/Release/RelNotes_en.html) Disclosed: 18/02/2013 VULNERABILITY DESCRIPTION: ========================== Alt-N WorldClient is prone to a username-enumeration weakness by querying the user's Free-Busy schedule. The DTSTART and DTEND parameters in the returned FBData.vfb file, may indicate whether an email address/username is valid or not. Attackers may exploit this weakness to discern valid usernames. This may aid them in brute-force password cracking or other attacks. Alt-N MDaemon v13.0.3 & v12.5.6 were tested and found vulnerable; other versions may also be affected. PoC Exploit: ============ http://www.example.com:3000/WorldClient.dll?View=fbinfo&User=mickey.mouse@xxxxxxxxxxxxxx For valid email accounts the DTSTART and DTEND values in the .vfb file start with a recent date backwards (e.g. 20120505) whereas for invalid ones the date is 19801231.
