From $URL :
Linux kernels built with Datagram Congestion Control Protocol(DCCP),
are vulnerable to a NULL pointer dereference flaw. This occurs while accessing socket options of
dccp_sock objects via ccid_hc_rx_getsockopt & ccid_hc_tx_getsockopt routines.
A privileged user/program could use this flaw to crash the kernel, resulting in DoS.
There are no longer any 2.x or <3.5.4 kernels available in the repository with
the exception of sys-kernel/xbox-sources which is unsupported by security.