festival_server in Centre for Speech Technology Research (CSTR) Festival, probably 2.0.95-beta and earlier, places a zero-length directory name in the LD_LIBRARY_PATH, which allows local users to gain privileges via a Trojan horse shared library in the current working directory.
Gentoo Linux Security Advisory 201312-6 - A vulnerability in Festival could result in arbitrary code execution, and privilege escalation. Versions prior to 2.1 are affected.