(RHSA-2011:1749) Low: libxml2 security and bug fix update

The libxml2 library is a development toolbox providing the implementation
of various XML standards. One of those standards is the XML Path Language
(XPath), which is a language for addressing parts of an XML document.

An off-by-one error, leading to a heap-based buffer overflow, was found in
the way libxml2 parsed certain XML files. A remote attacker could provide
a specially-crafted XML file that, when opened in an application linked
against libxml2, would cause the application to crash or, potentially,
execute arbitrary code with the privileges of the user running the
application. (CVE-2011-0216)

An integer overflow flaw, leading to a heap-based buffer overflow, was
found in the way libxml2 parsed certain XPath expressions. If an attacker
were able to supply a specially-crafted XML file to an application using
libxml2, as well as an XPath expression for that application to run against
the crafted file, it could cause the application to crash or, possibly,
execute arbitrary code. (CVE-2011-1944)

Multiple flaws were found in the way libxml2 parsed certain XPath
expressions. If an attacker were able to supply a specially-crafted XML
file to an application using libxml2, as well as an XPath expression for
that application to run against the crafted file, it could cause the
application to crash. (CVE-2010-4008, CVE-2010-4494, CVE-2011-2821,
CVE-2011-2834)

Note: Red Hat does not ship any applications that use libxml2 in a way that
would allow the CVE-2011-1944, CVE-2010-4008, CVE-2010-4494, CVE-2011-2821,
and CVE-2011-2834 flaws to be exploited; however, third-party applications
may allow XPath expressions to be passed which could trigger these flaws.

Red Hat would like to thank the Google Security Team for reporting the
CVE-2010-4008 issue. Upstream acknowledges Bui Quang Minh from Bkis as the
original reporter of CVE-2010-4008.

This update also fixes the following bugs:

• A number of patches have been applied to harden the XPath processing code
  in libxml2, such as fixing memory leaks, rounding errors, XPath numbers
  evaluations, and a potential error in encoding conversion. (BZ#732335)

All users of libxml2 are advised to upgrade to these updated packages,
which contain backported patches to correct these issues. The desktop must
be restarted (log out, then log back in) for this update to take effect.