Cyber Resilience

CVE-2023-22913

RCE in Zyxel Usg Flex 100 Firmware 4.50 – 5.35

RCECommand Injection
Published
24 April 2023
Modified
21 November 2024
Patch / advisory
View advisory
CVSS Score v3.1 8.1
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H
EPSS Score 0.013 68th percentile
Risk Priority 62 floored blend · peak EPSS

Summary

CVE-2023-22913 is a high-severity Command Injection (CWE-77) vulnerability in Zyxel Usg Flex 100 Firmware. Its CVSS base score is 8.1 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Command and Scripting Interpreter (T1059); ranked in the top 32% 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

A post-authentication command injection vulnerability in the “account_operator.cgi” CGI program of Zyxel USG FLEX series firmware versions 4.50 through 5.35, and VPN series firmware versions 4.30 through 5.35, which could allow a remote authenticated attacker to modify device configuration data,…

more

resulting in denial-of-service (DoS) conditions on an affected device.

CWE(s)
CWE-77

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 →
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 →
T1059.001 PowerShell Execution
Adversaries may abuse PowerShell commands and scripts for execution.
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 →
T1059.008 Network Device CLI Execution
Adversaries may abuse scripting or built-in command line interpreters (CLI) on network devices to execute malicious command and payloads.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2023-22914Same product: Zyxel Usg Flex 100
CVE-2023-22915Same product: Zyxel Usg Flex 100
CVE-2023-27991Same product: Zyxel Usg Flex 100
CVE-2023-28771Same product: Zyxel Usg Flex 100
CVE-2022-30525Same product: Zyxel Usg Flex 100W
CVE-2023-22917Same product: Zyxel Usg Flex 100
CVE-2023-22916Same product: Zyxel Usg Flex 100
CVE-2023-34139Same product: Zyxel Usg Flex 100
CVE-2023-27990Same product: Zyxel Usg Flex 100
CVE-2023-33009Same product: Zyxel Usg Flex 100

Affected Assets

zyxel
usg flex 100 firmware
4.50 — 5.35
zyxel
usg flex 100w firmware
4.50 — 5.35
zyxel
usg flex 200 firmware
4.50 — 5.35
zyxel
usg flex 50 firmware
4.50 — 5.35
zyxel
usg flex 50w firmware
4.50 — 5.35
zyxel
usg flex 500 firmware
4.50 — 5.35
zyxel
usg flex 700 firmware
4.50 — 5.35
zyxel
vpn100 firmware
4.50 — 5.35
zyxel
vpn1000 firmware
4.50 — 5.35
zyxel
vpn300 firmware
4.50 — 5.35
+1 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)
  • V1.2.3
  • V1.2.5
  • V1.2.8
  • V1.2.9

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

Secure SDLC practices directly require input validation and neutralization that prevent command injection.

DE.CM-09 partial match
prevents

Runtime monitoring of software and data can detect anomalous command execution resulting from injection.

ID.RA-01 partial match
prevents

Identifying recorded vulnerabilities enables remediation of command-injection flaws before exploitation.

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.8.28 Secure coding mostly match
prevents

Secure coding standards require proper escaping and parameterization of commands, directly eliminating CWE-77.

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

Security testing in development catches command-injection vulnerabilities before release.

A.8.25 Secure development life cycle partial match
prevents

Secure development life cycle mandates input validation and command construction practices that directly prevent command injection.

A.8.26 Application security requirements partial match
prevents

Application security requirements explicitly call for controls against injection flaws including command injection.

A.8.27 Secure system architecture and engineering principles partial match
prevents

Secure architecture principles reduce the attack surface but do not prescribe the specific neutralization techniques needed.

A.8.31 Separation of development, test and production environments none match
none

Environment separation limits the blast radius of an exploited command injection but does not prevent the flaw itself.

References