init in initramfs-tools 0.92f allows local users to overwrite arbitrary files via a symlink attack on the /tmp/initramfs.debug temporary file. NOTE: the vendor disputes this vulnerability, stating that "init is [used in] a single-user context; there's no possibility that this is exploitable.
https://bugs.gentoo.org/show_bug.cgi?id=235770
http://www.openwall.com/lists/oss-security/2008/10/30/2
http://dev.gentoo.org/~rbu/security/debiantemp/initramfs-tools