Bugtraq: Re: QPopper 4.0.x buffer overflow vulnerability

[Florian Heinz <heinz () cronon-ag de>]

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 ;)