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CERT Coordination Center

Zyxel P660 series modem/router denial of service vulnerability

Vulnerability Note VU#893726

Original Release Date: 2014-04-01 | Last Revised: 2014-04-01


Zyxel P660 series modem/router contains a denial of service vulnerability when parsing a high volume of SYN packets on the web management interface.


It has been reported that Zyxel P660 series modem/router (and possibly other models which share the same core firmware) fail to parse a high volume of SYN packets on the web management interface correctly causing the device to reboot. By default, the device runs a web management interface on port tcp/80 which is accessible remotely (LAN and WAN sides).


An unauthenticated attacker can cause the device to reboot and become unavailable by sending a stream of SYN packets to the device's web management interface.


We are currently unaware of a practical solution to this problem.

Restrict Network Access

As a general good security practice, only allow connections from trusted hosts and networks if possible. Restricting access would prevent an attacker from connecting to the service from a blocked network location.

Vendor Information


ZyXEL Affected

Notified:  June 17, 2013 Updated: July 31, 2013



Vendor Statement

We have not received a statement from the vendor.

Vendor Information

We are not aware of further vendor information regarding this vulnerability.

CVSS Metrics

Group Score Vector
Base 7.1 AV:N/AC:M/Au:N/C:N/I:N/A:C
Temporal 5.4 E:U/RL:U/RC:UC
Environmental 4.1 CDP:ND/TD:M/CR:ND/IR:ND/AR:ND



Thanks to Alex French for reporting this vulnerability.

This document was written by Michael Orlando.

Other Information

CVE IDs: CVE-2013-3588
Date Public: 2013-08-06
Date First Published: 2014-04-01
Date Last Updated: 2014-04-01 14:43 UTC
Document Revision: 11

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