XStream is a simple library to serialize objects to XML and back again.
It was found that XStream would deserialize arbitrary user-supplied XML content, thus representing objects of any type.
A remote attacker could pass a specially crafted XML document to XStream, possibly resulting in the execution of arbitrary code with the privileges of the process or a Denial of Service condition.
There is no known workaround at this time.
All XStream users should upgrade to the latest version:
# emerge --sync
# emerge --ask --oneshot --verbose ">=dev-java/xstream-1.4.8-r1"