A Computer Academic Underground advisory describes the
consequences of imwheel's handling of the process ID file (PID
file):
imwheel exclusively uses a predictably named PID file for
management of multiple imwheel processes. A race condition
exists when the -k command-line option is used to kill
existing imwheel processes. This race condition may be
used by a local user to Denial of Service another user
using imwheel, lead to resource exhaustion of the host
system, or append data to arbitrary files.