SSLeay.pm in libnet-ssleay-perl before 1.25 uses the /tmp/entropy file for entropy if a source is not set in the EGD_PATH variable, which allows local users to reduce the cryptographic strength of certain operations by modifying the file.
http://www.securityfocus.com/bid/13471
http://www.mandriva.com/security/advisories?name=MDKSA-2006:023