D-Bus is a daemon providing a framework for applications to communicate with one another.
schelte reported that the dbus_signature_validate() function can trigger a failed assertion when processing a message containing a malformed signature.
A local user could send a specially crafted message to the D-Bus daemon, leading to a Denial of Service.
There is no known workaround at this time.
All D-Bus users should upgrade to the latest version:
# emerge --sync
# emerge --ask --oneshot --verbose ">=sys-apps/dbus-1.2.3-r1"