bugtraq - Re: QPopper 4.0.x buffer overflow vulnerability

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Message-ID: <20030312095534.GB20261@dereference.de>
Date: Wed, 12 Mar 2003 10:55:34 +0100
From: Florian Heinz <heinz@...non-ag.de>
To: Torsten Mueller <torsten@...hesoft.de>
Subject: Re: QPopper 4.0.x buffer overflow vulnerability


On Wed, Mar 12, 2003 at 10:33:29AM +0100, Torsten Mueller wrote:
> 
> 
> Florian Heinz schrieb:
> > 
> > Hello,
> > 
> > Under certain conditions it is possible to execute arbitrary code using
> > a buffer overflow in the recent qpopper.
> > 
> > You need a valid username/password-combination and code is (depending on
> > the setup) usually executed with the user's uid and gid mail.
> > 
> ...
> > 
> > This is the short version. An enhanced version with error-checking,
> > bufsize- and return-address autodetection can be found on
> > http://nstx.dereference.de/snippets/qex.c
> > 
> > Feedback is welcome.
> 
> ... and here it comes ;-)
> 
> I tested http://nstx.dereference.de/snippets/qex.c
> against 3 selfcompiled qpopper4.0.4 on 3 different machines.
> 
> I can confirm, that on one machine "it worked", i got
> a shell.

Nice ;)

> More interesting for me is of course, if you can provide
> a patch against 4.0.4 to close this vulnerability.

As said, just make sure the buffer is null-terminated in Qvsnprintf().
Randall Gellens quickly reacted and released qpopper-4.0.5rc2, which
also contains a fix for this issue.
I also managed to modify a popper-binary with hexedit to use the
libc-vsnprintf instead of the Qvsnprintf provided, which solved that
problem, too, but this was merely for fun and testing, this could probably
cause other inconsistencies ;)