FreeBSD Security Advisory – A programming error in the OPIE library could allow an off-by-one buffer overflow to write a single zero byte beyond the end of an on-stack buffer.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/90013/FreeBSD-SA-10-05.opie.txt
Source: https://packetstormsecurity.com/files/90013/FreeBSD-Security-Advisory-OPIE-Off-By-One-Stack-Overflow.html