RC.BOOT in IBM AIX 5.1, 5.2, and 5.3 does not "use a secure location for temporary files," which allows local users to have an unknown impact, probably by overwriting files.
rmmlcachefile in bos.rte.install in AIX 5.1.0 through 5.3.0 allows local users to overwrite arbitrary files via a symlink attack on temporary files.