Hi,
Just checked my servers and all were vulnerable:
[zork@archdevel ~]$ sudoedit -s '' `perl -e 'print "A" x 65536'` malloc(): corrupted top size Aborted (core dumped)
Updating to the latest version (sudo-1.9.5.p2-1) closed this vulnerability. Maybe this should be posted as arch news message?
Regards, Łukasz