FreeBSD 4.1.1 and earlier, and possibly other BSD-based OSes, uses an insufficient random number generator to generate initial TCP sequence numbers (ISN), which allows remote attackers to spoof TCP connections.
Format string vulnerability in pw_error function in BSD libutil library allows local users to gain root privileges via a malformed password in commands such as chpass or passwd.
Buffer overflow in catopen() function in FreeBSD 5.0 and earlier, and possibly other OSes, allows local users to gain root privileges via a long environmental variable.
The catopen function in FreeBSD 5.0 and earlier, and possibly other OSes, allows local users to read arbitrary files via the LANG environmental variable.
The setlocale function in FreeBSD 5.0 and earlier, and possibly other OSes, allows local users to read arbitrary files via the LANG environmental variable.
The getnameinfo function in FreeBSD 4.1.1 and earlier, and possibly other operating systems, allows a remote attacker to cause a denial of service via a long DNS hostname.