libxml2 is the XML C parser and toolkit developed for the Gnome project.
A vulnerability in the xmlParserHandlePEReference() function of parser.c, when expanding entity references, can be exploited to consume large amounts of memory and cause a crash or hang.
A remote attacker may be able to cause Denial of Service via a specially crafted XML file containing malicious attributes.
There is no known workaround at this time.
All libxml2 users should upgrade to the latest version:
# emerge --sync
# emerge --ask --oneshot --verbose ">=dev-libs/libxml2-2.9.1-r4"