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Date: Thu, 19 Jul 2012 17:37:13 -0400 (EDT)
Subject: CVE-2012-4024 and CVE-2012-4025: Squashfs overflows

Hash: SHA1

We wanted to mention these two recent open-source CVEs here because
the upstream vendor expressed a position that the issues don't qualify
for CVE inclusion, and indicated that he often uses CVE in his work on
code unrelated to Squashfs.

This post isn't meant to suggest any level of urgency for Linux
distributions to produce new Squashfs packages. It's conceivable that
actual exploitation of these vulnerabilities will never occur

Although Squashfs is a Linux filesystem, these two CVEs are about a
utility program that is, in some ways, similar to tar or other archive
programs. In general, if an archive file might be obtained from an
untrusted remote source, and crafted data within the archive file
potentially leads to arbitrary code execution during extraction, the
issue can be included in CVE. There are many CVEs in this category
(e.g., see CVE-2011-1777 and CVE-2011-1778 in RHSA-2011:1507-1).
CVE-2012-4025 also fits into this category.

CVE-2012-4024 is different because the crafted data isn't in the
archive file. Specifically, the crafted data must be in a list file
that's similar to the list file used with the "tar -T" option. One
threat model is that an attacker announces 'We have created an example
of our project as a squashfs filesystem. The downloadable files are
myproject.sqsh and myproject.list. If you only want the source code,
you can extract it by running the "unsquashfs myproject.sqsh -ef
myproject.list" command.' If myproject.list is long enough (e.g.,
thousands of lines with reasonable source-code filenames and one line
with exploit code), probably most people wouldn't notice that the file
isn't legitimate.

Some similar issues involving archive programs don't qualify for CVE
inclusion because there is no plausible threat model. Ones that are
proposed occasionally include situations where a crafted filename must
be entered on the command line, and situations where the victim must
use a crafted configuration file.

- -- 
CVE assignment team, MITRE CVE Numbering Authority
M/S M300
202 Burlington Road, Bedford, MA 01730 USA
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