A “programming error” in fast_ipsec in FreeBSD 4.8-RELEASE through 6.1-STABLE and NetBSD 2 through 3 does not properly update the sequence number associated with a Security Association, which allows packets to pass sequence number checks and allows remote attackers to capture IPSec packets and conduct replay attacks.
ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-06:11.ipsec.asc
ftp://ftp.netbsd.org/pub/NetBSD/security/advisories/NetBSD-SA2006-011.txt.asc
secunia.com/advisories/19366
securitytracker.com/id?1015809
www.osvdb.org/24068
www.securityfocus.com/bid/17191
exchange.xforce.ibmcloud.com/vulnerabilities/25398