RHSA-2011:1749 - Security Advisory

Topic

Updated libxml2 packages that fix several security issues and various bugs
are now available for Red Hat Enterprise Linux 6.

The Red Hat Security Response Team has rated this update as having low
security impact. Common Vulnerability Scoring System (CVSS) base scores,
which give detailed severity ratings, are available for each vulnerability
from the CVE links in the References section.

Description

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.

Solution

Before applying this update, make sure all previously-released errata
relevant to your system have been applied.

This update is available via the Red Hat Network. Details on how to
use the Red Hat Network to apply this update are available at
https://access.redhat.com/kb/docs/DOC-11259

Affected Products

• Red Hat Enterprise Linux Server 6 x86_64
• Red Hat Enterprise Linux Server 6 i386
• Red Hat Enterprise Linux Server - Extended Life Cycle Support 6 x86_64
• Red Hat Enterprise Linux Workstation 6 x86_64
• Red Hat Enterprise Linux Workstation 6 i386
• Red Hat Enterprise Linux Desktop 6 x86_64
• Red Hat Enterprise Linux Desktop 6 i386
• Red Hat Enterprise Linux for IBM z Systems 6 s390x
• Red Hat Enterprise Linux for Power, big endian 6 ppc64
• Red Hat Enterprise Linux for Scientific Computing 6 x86_64
• Red Hat Enterprise Linux Server from RHUI 6 x86_64
• Red Hat Enterprise Linux Server from RHUI 6 i386
• Red Hat Enterprise Linux Server - Extended Life Cycle Support 6 i386
• Red Hat Enterprise Linux Server - Extended Life Cycle Support (for IBM z Systems) 6 s390x
• Red Hat Enterprise Linux Server - Extended Life Cycle Support Extension 6 x86_64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support Extension 6 i386
• Red Hat Enterprise Linux Server - Extended Life Cycle Support Extension (for IBM z Systems) 6 s390x

Fixes

• BZ - 645341 - CVE-2010-4008 libxml2: Crash (stack frame overflow or NULL pointer dereference) by traversal of XPath axis
• BZ - 665963 - CVE-2010-4494 libxml2: double-free in XPath processing code
• BZ - 709747 - CVE-2011-1944 libxml, libxml2: Heap-based buffer overflow by adding new namespace node to an existing nodeset or merging nodesets
• BZ - 724906 - CVE-2011-0216 libxml2: Off-by-one error leading to heap-based buffer overflow in encoding
• BZ - 732335 - Fix various problems and harden the XPath evaluation engine
• BZ - 735712 - CVE-2011-2821 libxml2: double free caused by malformed XPath expression in XSLT
• BZ - 735751 - CVE-2011-2834 libxml2: double-free caused by malformed XPath expression in XSLT

CVEs

• CVE-2011-0216
• CVE-2010-4008
• CVE-2011-1944
• CVE-2011-2834
• CVE-2011-2821
• CVE-2010-4494

References

• https://access.redhat.com/security/updates/classification/#low