The (1) fence_apc and (2) fence_apc_snmp programs, as used in (a) fence 2.02.00-r1 and possibly (b) cman, when running in verbose mode, allows local users to append to arbitrary files via a symlink attack on the apclog temporary file.
Exploitability
AV:LAC:MAu:NImpact
C:NI:PA:N1.9/AV:L/AC:M/Au:N/C:N/I:P/A:N