Zyxel Prestige SDSL Router IP Packet Length Remote Denial Of Service Vulnerability

Zyxel Prestige SDSL Router IP Packet Length Remote Denial Of Service Vulnerability

A problem with Zyxel routers has been discovered that could lead to a remote denial of service attack. The problem is in the receipt of malformed packets.

When a Zyxel router receives malformed packets crafted with an IP length shorter than the actual size of the packet, the router becomes unstable and drops connectivity. This loss of connectivity can last up to three minutes. This could lead to a remote user denying service to a legitimate user of the router. The router is affected only by malformed packets received through the DSL interface. Malformed packets sent through the LAN interface have no affect on the system.