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Vulnerability Assessment

Weakness
CWE
CWE-78
OWASP Top 10:2025
A05:2025 - Injection
ASVS 5.0
V1 - Encoding and Sanitization OS command sanitization, avoid shell exec
MITRE ATT&CK

2 techniques across 1 tactic: Execution

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

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Impact

CVSS score of 9.8 (CRITICAL). Attack characteristics: network attack vector, low complexity, no privileges required, no user interaction not required. Public proof-of-concept exploit code is available.
Exploit ScenarioDerived

A remote attacker could execute arbitrary operating system commands on the host by sending crafted requests to the affected application. No authentication is required to exploit this vulnerability.
Emergency Immediate action required. Why: CRITICAL + in CISA KEV (actively exploited), no patch available.
Exploited in the wild (CISA KEV) No patch listed yet 99.3% exploitation probability (EPSS)

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AnalysisAI

Improper error message handling in Zyxel ZyWALL/USG series firmware versions 4.60 through 4.73, VPN series firmware versions 4.60 through 5.35, USG FLEX series firmware versions 4.60 through 5.35,. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available and no vendor patch available.

RemediationAI

No vendor patch is available at time of analysis. Monitor vendor advisories for updates. Avoid passing user input to shell commands. Use language-specific APIs instead of shell execution. Apply strict input validation with allowlists.

Affects your stack

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Technical ContextAI · show details

This vulnerability is classified as OS Command Injection (CWE-78), which allows attackers to execute arbitrary operating system commands on the host. Improper error message handling in Zyxel ZyWALL/USG series firmware versions 4.60 through 4.73, VPN series firmware versions 4.60 through 5.35, USG FLEX series firmware versions 4.60 through 5.35, and ATP series firmware versions 4.60 through 5.35, which could allow an unauthenticated attacker to execute some OS commands remotely by sending crafted packets to an affected device. Affected products include: Zyxel Atp100 Firmware, Zyxel Atp100W Firmware, Zyxel Atp200 Firmware, Zyxel Atp500 Firmware, Zyxel Atp700 Firmware. Version information: through 4.73.

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  • Exploit and PoC references, threat intelligence from 22 sources
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Severity by source

Vendor (zyxel) PRIMARY 9.8 CRITICAL
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Primary rating from Vendor (zyxel) · only source for this CVE.

CVSS VectorVendor: zyxel

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

Lifecycle Timeline

2
Added to CISA KEV
Jul 14, 2026 - 04:22 CISA
CVE Published
Apr 25, 2023 - 02:15 cve.org
CRITICAL 9.8

DescriptionCVE.org

Improper error message handling in Zyxel ZyWALL/USG series firmware versions 4.60 through 4.73, VPN series firmware versions 4.60 through 5.35, USG FLEX series firmware versions 4.60 through 5.35, and ATP series firmware versions 4.60 through 5.35, which could allow an unauthenticated attacker to execute some OS commands remotely by sending crafted packets to an affected device.

Threat Intelligence Overview

EPSS Score
99.3%
Top 0% exploitable
CIRCL KEV
Listed
Community Exploited Vulnerability
Exploit
POC
Public exploit code exists
Data Quality
3 sources
Confidence: Low
NVD CVE.org CISA KEV EPSS POC (1) CIRCL

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity CRITICAL
CISA KEV Yes
Public POC Yes
EPSS 99.3%
Patch available No
Active threat Yes
Deciding rule
CRITICAL + in CISA KEV (actively exploited), no patch available
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Immediate
Exploitation· derived
Active
System Exposure· derived
Open
Automatable· derived
Yes
Human Impact· derived
High

Priority Score

233
Low Medium High Critical
KEV: +50
EPSS: +99
CVSS: +49
PoC: +20
Weaponized: +15
Threat intel: 0
Gov advisory: 0

Attack Technique

OS Command Injection CRITICAL

OS command injection occurs when an application passes unsanitized user input directly into system shell commands.

Affected Products (CPE)CVE.org

cpe:2.3:o:zyxel:atp100_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:atp100w_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:atp200_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:atp500_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:atp700_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:atp800_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:usg_flex_100_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:usg_flex_100w_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:usg_flex_200_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:usg_flex_50_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:usg_flex_500_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:usg_flex_50w_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:usg_flex_700_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:vpn100_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:vpn1000_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:vpn300_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:vpn50_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:zywall_usg_310_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:zywall_usg_310_firmware:4.73:-:*:*:*:*:*:*
cpe:2.3:o:zyxel:zywall_usg_100_firmware:*:*:*:*:*:*:*:*
+ 1 more

Same weakness CWE-78 – OS Command Injection

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CVE-2020-9054 CRITICAL POC
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CVE-2017-6334 HIGH POC
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CVE-2024-50603 CRITICAL POC
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Same technique Command Injection

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CVE-2024-21887 CRITICAL POC
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CVE-2016-3081 HIGH POC
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CVE-2012-1823 CRITICAL POC
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CVE-2016-1555 CRITICAL POC
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CVE-2024-55956 CRITICAL POC
9.8

References

Advisories & patches
ADVISORY https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-remote-command-injection-vulnerability-of-firewalls REF https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2023-28771

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