ZyXEL P-660HW-T1 2 devices with ZyNOS firmware 3.40(AXH.0), PMG5318-B20A devices with firmware 1.00AANC0b5, and NBG-418N devices have a default password of 1234 for the admin account, which allows remote attackers to obtain administrative access via unspecified vectors.

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), support authentication over HTTP via a hash string in the hiddenPassword field, which allows remote attackers to obtain access via a replay attack.

ZyXEL Prestige routers have a minimum password length for the admin account that is too small, which makes it easier for remote attackers to guess passwords via brute force methods.

ZyXEL Prestige routers, including P-660, P-661, and P-662 models with firmware 3.40(AGD.2) through 3.40(AHQ.3), allow remote authenticated users to obtain ISP and Dynamic DNS credentials by sending a direct request for (1) WAN.html, (2) wzPPPOE.html, and (3) rpDyDNS.html, and then reading the HTML source.

ZyXEL Prestige routers, including P-660 and P-661 models with firmware 3.40(AGD.2) through 3.40(AHQ.3), have (1) "user" as their default password for the "user" account and (2) "1234" as their default password for the "admin" account, which makes it easier for remote attackers to obtain access.

The SNMP service on ZyXEL Prestige routers, including P-660 and P-661 models with firmware 3.40(AGD.2) through 3.40(AHQ.3), has "public" as its default community for both (1) read and (2) write operations, which allows remote attackers to perform administrative actions via SNMP, as demonstrated by reading the Dynamic DNS service password or inserting an XSS sequence into the system.sysName.0 variable, which is displayed on the System Status page.

ZyXEL Prestige routers, including P-660 and P-661 models with firmware 3.40(AGD.2) through 3.40(AHQ.3), allow remote authenticated users to gain privileges by accessing administrative URIs, as demonstrated by rpSysAdmin.html.

The default SNMP configuration on ZyXEL Prestige routers, including P-660 and P-661 models with firmware 3.40(AGD.2) through 3.40(AHQ.3), has a Trusted Host value of 0.0.0.0, which allows remote attackers to send SNMP requests from any source IP address.

ZyXEL Prestige routers, including P-660, P-661, and P-662 models with firmware 3.40(AGD.2) through 3.40(AHQ.3), allow remote authenticated users to obtain authentication data by making direct HTTP requests and then reading the HTML source, as demonstrated by a request for (1) RemMagSNMP.html, which discloses SNMP communities; or (2) WLAN.html, which discloses WEP keys.

ZynOS 3.40 allows remote attackers to cause a denial of service (link restart) by sending a request for the name \M via the SMB Mail Slot Protocol.