Bug#560951: CVE-2009-3560 and CVE-2009-3720 denial-of-services

[Michael Gilbert]

package: python-xml
severity: serious
tags: security

Hi,

The following CVE (Common Vulnerabilities & Exposures) ids were
published for expat.  I have determined that this package embeds a
vulnerable copy of xmlparse.c and xmltok_impl.c.  However, since this is
a mass bug filing (due to so many packages embedding expat), I have
not had time to determine whether the vulnerable code is actually
present in any of the binary packages derived from this source package.
Please determine whether this is the case. If the binary packages are
not affected, please feel free to close the bug with a message
containing the details of what you did to check.

CVE-2009-3560[0]:
| The big2_toUtf8 function in lib/xmltok.c in libexpat in Expat 2.0.1,
| as used in the XML-Twig module for Perl, allows context-dependent
| attackers to cause a denial of service (application crash) via an XML
| document with malformed UTF-8 sequences that trigger a buffer
| over-read, related to the doProlog function in lib/xmlparse.c, a
| different vulnerability than CVE-2009-2625 and CVE-2009-3720.

CVE-2009-3720[1]:
| The updatePosition function in lib/xmltok_impl.c in libexpat in Expat
| 2.0.1, as used in Python, PyXML, w3c-libwww, and other software,
| allows context-dependent attackers to cause a denial of service
| (application crash) via an XML document with crafted UTF-8 sequences
| that trigger a buffer over-read, a different vulnerability than
| CVE-2009-2625.

These issues also affect old versions of expat, so this package in etch
and lenny is very likely affected.  This is a low-severity security
issue, so DSAs will not be issued to correct these problems.  However,
you can optionally submit a proposed-update to the release team for
inclusion in the next stable point releases.  If you plan to do this, 
please open new bugs and include the security tag so we are aware that
you are working on that.

For further information see [0],[1],[2],[3].  In particular, [2] and [3]
are links to the patches for CVE-2009-3560 and CVE-2009-3720 respectively.
Note that the ideal solution would be to make use of the system expat so
only one package will need to be updated for future security issues.
Preferably in your update to unstable, alter your package to make use of
the system expat.

If you fix the vulnerability please also make sure to include the
CVE id in your changelog entry.

[0] http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2009-3560
    http://security-tracker.debian.org/tracker/CVE-2009-3560
[1] http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2009-3720
    http://security-tracker.debian.org/tracker/CVE-2009-3720
[2] http://expat.cvs.sourceforge.net/viewvc/expat/expat/lib/xmlparse.c?r1=1.164&r2=1.165
[3] http://expat.cvs.sourceforge.net/viewvc/expat/expat/lib/xmltok_impl.c?r1=1.13&r2=1.15&view=patch