Zyxel · Multiple Products
CVE-2020-29583
Zyxel Multiple Products Use of Hard-Coded Credentials Vulnerability
What it is
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.
CISA: Zyxel firewalls (ATP, USG, VM) and AP Controllers (NXC2500 and NXC5500) contain a use of hard-coded credentials vulnerability in an undocumented account ("zyfwp") with an unchangeable password.
What to do
Apply updates per vendor instructions.
Deadline for US federal agencies: May 3, 2022
- Added to the CISA list
- November 3, 2021
- Published
- December 22, 2020
- Severity
- Critical 9.8 CVSS 3.1
- Chance of attacks in the next 30 days (EPSS)
- 90% in the top 0.2% of all known vulnerabilities
- Weakness
- CWE-522
- More details
- NVD · CVE.org · CISA
All references (7)
- 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/5254/whats-new-for-zld4-60-patch-1-available-on-dec-15
- https://businessforum.zyxel.com/discussion/5252/zld-v4-60-revoke-and-wk48-firmware-release
- https://www.eyecontrol.nl/blog/undocumented-user-account-in-zyxel-products.html
- https://www.zyxel.com/support/CVE-2020-29583.shtml
- https://www.secpod.com/blog/a-secret-zyxel-firewall-and-ap-controllers-could-allow-for-administrative-access-…
More exploited flaws from Zyxel
| Added | Vulnerability | Product | Severity | Attack chance |
|---|---|---|---|---|
| Sep 21, 2026 | Stack-Based Buffer Overflow | GS1900 Series Switches | High 8.8 | 2.8% |
| Feb 11, 2025 | DSL CPE OS Command Injection | DSL CPE Devices | High 8.8 | 21% |
| Feb 11, 2025 | DSL CPE OS Command Injection | DSL CPE Devices | High 8.8 | 23% |
| Dec 3, 2024 | Path Traversal | Multiple Firewalls | High 7.5 | 2.9% |
| Sep 18, 2023 | Command Injection | EMG2926 Routers | High 8.8 | 33% |
| Aug 7, 2023 | Command Injection | P660HN-T1A Routers | Critical 9.8 | 95% |
| Jun 23, 2023 | Multiple NAS Devices Command Injection | Multiple Network-Attached Storage (NAS) Devices | Critical 9.8 | 82% |
| Jun 5, 2023 | Buffer Overflow | Multiple Firewalls | Critical 9.8 | 28% |
Sources: Known Exploited Vulnerabilities (CISA, public domain), CVE records (cve.org) and EPSS (FIRST). The chance of attacks is the EPSS estimate that someone will try to exploit the flaw in the next 30 days.