CISA KEV catalog
Confirmed active exploitation.
Listed in CISA's catalog of Known Exploited Vulnerabilities: attackers are using it in real attacks. Patch it with priority.
- Name
- Zyxel Multiple Products Use of Hard-Coded Credentials Vulnerability
- Added to catalog
- Remediation due date (US federal)
- Required action
- Apply updates per vendor instructions.
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: usg20-vpn firmware; zyxel: usg20-vpn; zyxel: usg20w-vpn firmware; zyxel: usg20w-vpn; zyxel: usg40 firmware; zyxel: usg40; zyxel: usg40w firmware; zyxel: usg40w; zyxel: usg60 firmware; zyxel: usg60; zyxel: usg60w firmware; zyxel: usg60w; zyxel: usg110 firmware; zyxel: usg110; zyxel: usg210 firmware
References10
- www.zyxel.com/support/CVE-2020-29583.shtml Vendor Advisory
- www.zyxel.com/support/security_advisories.shtml Vendor Advisory
- www.zyxel.com/support/CVE-2020-29583.shtml Vendor Advisory
- www.zyxel.com/support/security_advisories.shtml Vendor Advisory
- www.secpod.com/blog/a-secret-zyxel-firewall-and-ap-controllers-… ExploitThird Party Advisory
- www.secpod.com/blog/a-secret-zyxel-firewall-and-ap-controllers-… ExploitThird Party Advisory
- ftp.zyxel.com/USG40/firmware/USG40_4.60%28AALA.1%29C0_2.pdf Broken Link
- businessforum.zyxel.com/discussion/5252/zld-v4-60-revoke-and-wk… Release Notes
- businessforum.zyxel.com/discussion/5254/whats-new-for-zld4-60-p… Release Notes
- www.eyecontrol.nl/blog/undocumented-user-account-in-zyxel-produ… Broken LinkThird Party Advisory
Metrics
- CVSS 3.1
-
9.8
CRITICAL
Score source: NVD
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - EPSS — exploit probability
- 90% percentile: 100 · as of 2 November 2026
- CWE
- CWE-522
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