libxml2 -- An off-by-one out-of-bounds write by XPointer

Google chrome team reports:

An off-by-one out-of-bounds write flaw was found in the way libxml, a library
for providing XML and HTML support, evaluated certain XPointer parts (XPointer
is used by libxml to include only the part from the returned XML document, that
can be accessed using the XPath expression given with the XPointer). A remote
attacker could provide a specially-crafted XML file, which once opened in an
application, linked against libxml, would lead to that application crash, or,
potentially arbitrary code execution with the privileges of the user running
the application.
Note: The flaw to be exploited requires the particular application, linked
against libxml, to use the XPointer evaluation functionality.