Cyber Resilience

CVE-2023-27991

RCE in Zyxel Atp200 Firmware 4.32 – 5.36

RCECommand Injection
Published
24 April 2023
Modified
21 November 2024
Patch / advisory
View advisory
CVSS Score v3.1 8.8
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
EPSS Score 0.015 72th percentile
Risk Priority 68 floored blend · peak EPSS

Summary

CVE-2023-27991 is a high-severity OS Command Injection (CWE-78) vulnerability in Zyxel Atp200 Firmware. Its CVSS base score is 8.8 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Command and Scripting Interpreter (T1059); ranked in the top 28% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.

OWASP Top 10 for Web (2025)

A05:2025 Injection

EU & UK References

Vulnerability Data

The post-authentication command injection vulnerability in the CLI command of Zyxel ATP series firmware versions 4.32 through 5.35, USG FLEX series firmware versions 4.50 through 5.35, USG FLEX 50(W) firmware versions 4.16 through 5.35, USG20(W)-VPN firmware versions 4.16 through 5.35,…

more

and VPN series firmware versions 4.30 through 5.35, which could allow an authenticated attacker to execute some OS commands remotely.

CWE(s)
CWE-78

Related Threats

MITRE ATT&CK Enterprise Techniques

T1059 Command and Scripting Interpreter Execution
Adversaries may abuse command and script interpreters to execute commands, scripts, or binaries.
attack.mitre.org →
T1059.003 Windows Command Shell Execution
Adversaries may abuse the Windows command shell for execution.
attack.mitre.org →
T1059.004 Unix Shell Execution
Adversaries may abuse Unix shell commands and scripts for execution.
attack.mitre.org →
T1059.001 PowerShell Execution
Adversaries may abuse PowerShell commands and scripts for execution.
attack.mitre.org →
T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2023-28771Same product: Zyxel Atp100
CVE-2022-30525Same product: Zyxel Atp100
CVE-2024-42057Same product: Zyxel Atp100
CVE-2024-42060Same product: Zyxel Atp100
CVE-2024-42059Same product: Zyxel Atp100
CVE-2025-8078Same product: Zyxel Atp100
CVE-2024-7203Same product: Zyxel Atp100
CVE-2023-6398Same product: Zyxel Atp100
CVE-2023-34139Same product: Zyxel Usg Flex 100
CVE-2020-9054Same product: Zyxel Atp100

Affected Assets

zyxel
atp200 firmware
4.32 — 5.36
zyxel
atp100 firmware
4.32 — 5.36
zyxel
atp700 firmware
4.32 — 5.36
zyxel
atp500 firmware
4.32 — 5.36
zyxel
atp100w firmware
4.32 — 5.36
zyxel
atp800 firmware
4.32 — 5.36
zyxel
usg flex 100 firmware
4.50 — 5.36
zyxel
usg flex 50 firmware
4.50 — 5.36
zyxel
usg flex 200 firmware
4.50 — 5.36
zyxel
usg flex 500 firmware
4.50 — 5.36
+9 more product configuration(s) — see NVD for full list

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)

—

Validate
Prove the fix (OWASP ASVS)
  • V1.2.5
  • V1.2.8
  • V15.2.5

Likely Mitigating Controls AI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

SC-27 Platform-independent Applications
addresses: CWE-78

Platform-independent apps typically execute inside a managed runtime or sandbox that restricts direct OS command execution, reducing the ability to exploit OS command injection.

SI-10 Information Input Validation
addresses: CWE-78

Validates inputs to block special elements that would alter OS command execution.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match
prevents

PR.PS-06's SDLC practices directly require secure coding and input handling that blocks command-injection defects, yet the single broad outcome leaves many specific neutralization vectors and verification gaps unaddressed.

PR.PS-02 partial match
prevents

Routine patching/maintenance can remediate known command-injection CVEs in dependencies (partial forward) but does nothing to stop developers from introducing improper neutralization in custom code (none reverse).

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.29 Security testing in development and acceptance mostly match
finds

Security testing and code review target insecure use of operating-system command interfaces, catching command-injection flaws introduced during development.

References