ZyXEL P-660HW v3 devices allow remote attackers to cause a denial of service (router unreachable/unresponsive) via a flood of fragmented UDP packets.
ZyXEL P-660HW v3 devices allow remote attackers to cause a denial of service (CPU consumption) via a flood of IP packets with a TTL of 1.
ZyXEL Prestige routers, including P-660, P-661, and P-662 models with firmware 3.40(PE9) and 3.40(AGD.2) through 3.40(AHQ.3), do not use a salt when calculating an MD5 password hash, which makes it easier for attackers to crack passwords.