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Re: QPopper 4.0.x buffer overflow vulnerability
From: Florian Heinz <heinz () cronon-ag de>
Date: Wed, 12 Mar 2003 10:55:34 +0100

On Wed, Mar 12, 2003 at 10:33:29AM +0100, Torsten Mueller wrote:

Florian Heinz schrieb:


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

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 ;)

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