The (1) red_channel_pipes_add_type and (2) red_channel_pipes_add_empty_msg functions in server/red_channel.c in SPICE before 0.12.4 do not properly perform ring loops, which might allow remote attackers to cause a denial of service (reachable assertion and server exit) by triggering a network error.
https://bugzilla.redhat.com/show_bug.cgi?id=984769
http://www.ubuntu.com/usn/USN-1926-1
http://www.debian.org/security/2014/dsa-2839
http://seclists.org/oss-sec/2013/q3/115
http://rhn.redhat.com/errata/RHSA-2013-1260.html
http://cgit.freedesktop.org/spice/spice/commit/?id=53488f0275d6c8a121af49f7ac817d09ce68090d