ZyXEL ZyWALL USG 2.12 AQQ.2 and 3.30 AQQ.7 devices are affected by a CSRF vulnerability via a cgi-bin/zysh-cgi cmd action to add a user account. This account's access could, for example, subsequently be used for stored XSS.

ZyXEL VMG3312-B10B 1.00(AAPP.7) devices have a backdoor root account with the tTn3+Z@!Sr0O+ password hash in the etc/default.cfg file.

Zyxel VMG3312 B10B devices are affected by a persistent XSS vulnerability via the pages/connectionStatus/connectionStatus-hostEntry.cmd hostname parameter.

ZyXEL ZyWALL/USG series devices have a Bleichenbacher vulnerability in their Internet Key Exchange (IKE) handshake implementation used for IPsec based VPN connections.

The Zyxel Multy X (AC3000 Tri-Band WiFi System) device doesn't use a suitable mechanism to protect the UART. After an attacker dismantles the device and uses a USB-to-UART cable to connect the device, he can use the 1234 password for the root account to login to the system. Furthermore, an attacker can start the device's TELNET service as a backdoor.

This vulnerability allows remote attackers to cause a denial-of-service condition on vulnerable installations of ZyXEL P-870H-51 DSL Router 1.00(AWG.3)D5. Authentication is not required to exploit this vulnerability. The specific flaw exists within numerous exposed CGI endpoints. The vulnerability is caused by improper access controls that allow access to critical functions without authentication. An attacker can use this vulnerability to reboot affected devices, along with other actions. Was ZDI-CAN-4540.

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 NBG6716 V1.00(AAKG.9)C0 devices allow command injection in the ozkerz component because beginIndex and endIndex are used directly in a popen call.

ZyXEL NWA1100-N, NWA1100-NH, NWA1121-NI, NWA1123-AC, and NWA1123-NI access points; P-660HN-51, P-663HN-51, VMG1312-B10A, VMG1312-B30A, VMG1312-B30B, VMG4380-B10A, VMG8324-B10A, VMG8924-B10A, VMG8924-B30A, and VSG1435-B101 DSL CPEs; PMG5318-B20A GPONs; SBG3300-N000, SBG3300-NB00, and SBG3500-N000 small business gateways; GS1900-8 and GS1900-24 switches; and C1000Z, Q1000, FR1000Z, and P8702N project models use non-unique X.509 certificates and SSH host keys.