jail.c in jail in FreeBSD 8.0 and 8.1-PRERELEASE, when the "-l -U root" options are omitted, does not properly restrict access to the current working directory, which might allow local users to read, modify, or create arbitrary files via standard filesystem operations.
http://www.vupen.com/english/advisories/2010/1247
http://www.securityfocus.com/bid/40399
http://securitytracker.com/id?1024038
http://security.FreeBSD.org/advisories/FreeBSD-SA-10:04.jail.asc