Date: Sat, 14 Oct 2000 04:03:13 +0200 From: Robert van der Meulen <rvdm@CISTRON.NL> Subject: Re: another Xlib buffer overflow To: BUGTRAQ@SECURITYFOCUS.COM Quoting Michal Zalewski (lcamtuf@dione.ids.pl): > On Sat, 14 Oct 2000, Robert van der Meulen wrote: > > ii xserver-svga 3.3.6-10 X server for SVGA graphics cards > > <rvdm@crypt:~> export DISPLAY=`perl -e '{print "0" x 128}'` > Couldn't see ':' there. It's late at night, and i'm stupid ;) I've been looking a bit further into this. This actually _does_ trigger segfaults on both woody and potato. The problem is, that the display number can only contain numeric values (Xlib does check _that_). This seriously limits possibilities for inserting shellcode. With only the hexvalues of '0' to '9' an actual shellcode isn't possible, but jumping to different addresses is possible. Greets, Robert van der Meulen / Emphyrio -- | rvdm@cistron.nl - Cistron Internet Services - www.cistron.nl | | php3/c/perl/html/c++/sed/awk/linux/sql/cgi/security | | My statements are mine, and not necessarily cistron's. | Marijuana is nature's way of saying, "Hi!".