D-Bus before 1.15.6 sometimes allows unprivileged users to crash dbus-daemon. If a privileged user with control over the dbus-daemon is using the org.freedesktop.DBus.Monitoring interface to monitor message bus traffic, then an unprivileged user with the ability to connect to the same dbus-daemon can cause a dbus-daemon crash under some circumstances via an unreplyable message. When done on the well-known system bus, this is a denial-of-service vulnerability. The fixed versions are 1.12.28, 1.14.8, and 1.15.6.