What’s Vulnerable › Vulnerabilities

CVE-2020-29583: Zyxel Multiple Products Use of Hard-Coded Credentials Vulnerability

• Severity: critical (CVSS 9.8 v3.1)
• Exploited in the wild: yes — in CISA KEV since 2021-11-03
• EPSS: 90.2% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2020-12-22 · updated 2026-06-17
• Weakness: CWE-522

Description

Firmware version 4.60 of Zyxel USG devices contains an undocumented account (zyfwp) with an unchangeable password. The password for this account can be found in cleartext in the firmware. This account can be used by someone to login to the ssh server or web interface with admin privileges.

Affected products

• Zyxel Atp100 Firmware: 4.60
• Zyxel Atp100W Firmware: 4.60
• Zyxel Atp200 Firmware: 4.60
• Zyxel Atp500 Firmware: 4.60
• Zyxel Atp700 Firmware: 4.60
• Zyxel Atp800 Firmware: 4.60
• Zyxel Usg1100 Firmware: 4.60
• Zyxel Usg110 Firmware: 4.60
• Zyxel Usg1900 Firmware: 4.60
• Zyxel Usg20-Vpn Firmware: 4.60
• Zyxel USG20(W)-VPN firmware: 4.60
• Zyxel Usg210 Firmware: 4.60
• Zyxel Usg2200 Firmware: 4.60
• Zyxel Usg310 Firmware: 4.60
• Zyxel Usg40 Firmware: 4.60
• Zyxel Usg40W Firmware: 4.60
• Zyxel Usg60 Firmware: 4.60
• Zyxel Usg60W Firmware: 4.60
• Zyxel firewall (ZLD): 4.60
• Zyxel USG FLEX 100(W) firmware: 4.60
• Zyxel USG FLEX 200 firmware: 4.60
• Zyxel USG FLEX 500 firmware: 4.60
• Zyxel USG FLEX 700 firmware: 4.60
• Zyxel Vpn1000 Firmware: 4.60
• Zyxel Vpn100 Firmware: 4.60
• Zyxel Vpn300 Firmware: 4.60
• Zyxel Vpn50 Firmware: 4.60
• Zyxel Zywall1100 Firmware: 4.60
• Zyxel Zywall110 Firmware: 4.60
• Zyxel Zywall310 Firmware: 4.60

References

• http://ftp.zyxel.com/USG40/firmware/USG40_4.60%28AALA.1%29C0_2.pdf
• https://businessforum.zyxel.com/discussion/5252/zld-v4-60-revoke-and-wk48-firmware-release
• https://businessforum.zyxel.com/discussion/5254/whats-new-for-zld4-60-patch-1-available-on-dec-15
• https://www.eyecontrol.nl/blog/undocumented-user-account-in-zyxel-products.html
• https://www.secpod.com/blog/a-secret-zyxel-firewall-and-ap-controllers-could-allow-for-administrative-access-cve-2020-29583/
• https://www.zyxel.com/support/CVE-2020-29583.shtml
• https://www.zyxel.com/support/security_advisories.shtml
• http://ftp.zyxel.com/USG40/firmware/USG40_4.60%28AALA.1%29C0_2.pdf
• https://businessforum.zyxel.com/discussion/5252/zld-v4-60-revoke-and-wk48-firmware-release
• https://businessforum.zyxel.com/discussion/5254/whats-new-for-zld4-60-patch-1-available-on-dec-15
• https://www.eyecontrol.nl/blog/undocumented-user-account-in-zyxel-products.html
• https://www.secpod.com/blog/a-secret-zyxel-firewall-and-ap-controllers-could-allow-for-administrative-access-cve-2020-29583/

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