CVE-2020-29583

CRITICAL
9.8
CVSS Score
Published: December 22, 2020 at 12:00 AM UTC
Updated: June 17, 2026 at 03:11 AM UTC
60 products affected across 1 vendorUsg Flex 100W FirmwareUSG FLEX 200 firmwareUSG FLEX 700 firmware

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Severity
CRITICAL9.8
Exploitation
CISA KEV
Exploit prediction
EPSS 90%
SSVC
Active

Actively Exploited

CISA Known Exploited Vulnerabilities (KEV) Catalog

EPSS Score90.2%

EPSS (Exploit Prediction Scoring System) estimates a 90.2% chance this CVE is exploited in the wild within the next 30 days — higher than 100% of all CVEs. It complements CVSS: a high EPSS on a mid-severity CVE can still be urgent.

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.

Required Action
Apply updates per vendor instructions.
Ransomware Use
Unknown
Added to KEV
Nov 3, 2021
Remediation Due
May 3, 2022
1639 days overdue

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

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

zyxel-atp100w (same device)
zyxel-atp200 (same device)
zyxel-atp500 (same device)
zyxel-atp700 (same device)
zyxel-atp800 (same device)
zyxel-usg-flex-100 (same device)
zyxel-usg-flex-100w (same device)
zyxel-usg-flex-200 (same device)

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

SSVC — Action Prioritization

SSVCActiveAutomatableTotal impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

9.8CRITICALCISA-ADP
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
HIGH
Vector?

Quick Info

StatusANALYZED
CWE
CWE-522

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