The OPVPWrapper::loadDriver function in oprs/OPVPWrapper.cxx in the pdftoopvp filter in CUPS and cups-filters before 1.0.47 allows local users to gain privileges via a Trojan horse driver in the same directory as the PDF file.
https://bugzilla.redhat.com/show_bug.cgi?id=1027551
http://www.ubuntu.com/usn/USN-2144-1
http://www.ubuntu.com/usn/USN-2143-1
http://www.debian.org/security/2014/dsa-2876
http://www.debian.org/security/2014/dsa-2875
http://bzr.linuxfoundation.org/loggerhead/openprinting/cups-filters/revision/7176