We received the following report.
The issue is public.

The mentioned attachment was not included as we didn't receive the
original mail but as upstream apparently was notified they may have
it.

From djb@cr.yp.to Wed Dec 15 14:21:33 2004
Date: 15 Dec 2004 08:20:11 -0000
From: D. J. Bernstein <djb@cr.yp.to>
To: securesoftware@list.cr.yp.to, cups@easysw.com
Subject: [remote] [control] CUPS 1.1.22 hpgltops ParseCommand overflows buf

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

A CUPS installation is at risk whenever it prints an HPGL file obtained
from email (or a web page or any other source that could be controlled
by an attacker). You are at risk if you print data through a CUPS
installation at risk. The source of the HPGL file has complete control
over the CUPS ``lp'' account; in particular, he can read and modify the
files you are printing.

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

   cd /usr/ports/print/cups
   make install

to download and compile the CUPS package, version 1.1.22 (current).
Then, as any user, save the file 21.hpgl.gz attached to this message,
and type

   gunzip 21.hpgl
   /usr/local/libexec/cups/filter/hpgltops \
   15 $USER test-title 1 none 21.hpgl > 21.ps

with the unauthorized result that a file named x is removed from the
current directory. (I tested this with a 541-byte environment, as
reported by printenv | wc -c.)

Here's the bug: In hpgl-input.c, ParseCommand() reads any number of
bytes into a 262144-byte buf[] array.

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

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