Hello everyone, A while ago I found a flaw in ICQ which I believe to be fairly serious and asked whom to notify. Thanks for everyone's assistance in this. :-) I notified Mirabilis and they have totally failed to respond (I've waited about 2 weeks), so I'll now submit it here. It's a very simple flaw. At present I've only tested on the Win32 ICQ 98a 1.30 version, and have not tested on ICQ99 nor on other platforms. Here is how it works : When a person is sending a file to another user on ICQ, the person receiving the file has a window pop up which shows the filename, a description entered by the sender, and options of where to save or not save etc. I've found there isn't a check on the length of the filename being sent. The pane in the pop-up window will display as much of the filename as it can, and if the filename is longer that the pane, the ending remainder won't be displayed. Therefore a simple attack is possible, sending a file named (for example) : "leah2.jpg .exe" will display leah2.jpg to the receiving user whom will only see "leah2.jpg" in the pop-up window and assume it is a harmless picture file for example, not executable code. This is very bad considering ICQ has the option of 'OPEN'ing the file once the transfer is completed. Many people do this to have the picture displayed to them (by the program associated with the extension). In the case of this exploit, the executable code will be run instead of the program the victim is expecting. A craftily coded program would be able to do both so as to avoid suspicion on the part of the victim. One thing I have noted in testing is that on one person's system running Win95 this did not work. His computer renamed the file to .zip on receiving which stopped the file executing. I don't know why and as far as I have been able to find out (I haven't had physical access to his PC) this is due to his personal configuration and is not the norm. One additional thing should considered also, and I don't yet have the time and ability to do so; is a buffer overflow exploit present here or in other versions which allows remote automatic code execution? This depends on the program and the protocol, of course. It could be *very* bad. Regards and best wishes, + Justin Clift Digital Distribution www.digitaldistribution.com
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