CriticalCVE-2022-30525

    Zyxel Multiple Firewalls OS Command Injection Vulnerability (CVE-2022-30525)

    Published In CISA KEV since Sources: CVE.org

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    What is affected, what to do

    A OS command injection vulnerability in the CGI program of Zyxel USG FLEX 100(W) firmware versions 5.00 through 5.21 Patch 1, USG FLEX 200 firmware versions 5.00 through 5.21 Patch 1, USG FLEX 500 firmware versions 5.00 through 5.21 Patch 1, USG FLEX 700 firmware versions 5.00 through 5.21 Patch 1, USG FLEX 50(W) firmware versions 5.10 through 5.21 Patch 1, USG20(W)-VPN firmware versions 5.10 through 5.21 Patch 1, ATP series firmware versions 5.10 through 5.21 Patch 1, VPN series firmware versions 4.60 through 5.21 Patch 1, which could allow an attacker to modify specific files and then execute some OS commands on a vulnerable device.

    The vulnerability is being actively exploited; treat it as a priority. The available sources name no fixed version. Check the vendor guidance in the references below. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • Zyxel USG FLEX 100(W) firmware eq 5.00 through 5.21 Patch 1..5.00 through 5.21 Patch 1
    • Zyxel USG FLEX 200 firmware eq 5.00 through 5.21 Patch 1..5.00 through 5.21 Patch 1
    • Zyxel USG FLEX 500 firmware eq 5.00 through 5.21 Patch 1..5.00 through 5.21 Patch 1
    • Zyxel USG FLEX 700 firmware eq 5.00 through 5.21 Patch 1..5.00 through 5.21 Patch 1
    • Zyxel ATP series firmware eq 5.10 through 5.21 Patch 1..5.10 through 5.21 Patch 1
    • Zyxel VPN series firmware eq 4.60 through 5.21 Patch 1..4.60 through 5.21 Patch 1
    • Zyxel USG FLEX 50(W) firmware eq 5.10 through 5.21 Patch 1..5.10 through 5.21 Patch 1
    • Zyxel USG 20(W)-VPN firmware eq 5.10 through 5.21 Patch 1..5.10 through 5.21 Patch 1

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    9.8

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: NVD, CVSS v3

    9.8

    CVSS v3

    Severity Critical on the scale from 0 to 10.

    Source: CVE.org

    99.94 %

    EPSS score

    High — model estimates ≥ 50% chance of real-world exploitation within 30 days.

    Source: FIRST EPSS, percentile 99.97

    Show all metrics
    Severity
    Critical
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    229.74 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

    Read in glossary
    actively exploited
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    9.8 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    9.8
    EPSS score

    The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.

    Read in glossary
    99.94 %
    High — model estimates ≥ 50% chance of real-world exploitation within 30 days.
    EPSS percentile

    The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.

    Read in glossary
    99.97
    Critical — this CVE ranks in the top fifth of all CVEs scored today (rank ≥ 80%).
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    Actively exploited
    Published
    In CISA KEV since

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    CISA assessment (SSVC)
    Exploitation: active · automatable · Technical impact: total
    Source: CISA Vulnrichment, as of 29 January 2025
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-78

    Response and mitigation

    Why act now?

    Prioritisation rationale

    This CVE is on KEV because it hands an unauthenticated attacker remote code execution on the perimeter device itself — the worst possible blast radius, since the compromised firewall then becomes a VPN pivot, traffic sniffer and TLS man-in-the-middle. Exploitation likelihood ranks among the very highest in the entire CVE catalogue; mass-scanning for /ztp/cgi-bin/handler has been running continuously since May 2022 and is used by both botnet operators (Mirai variants) and initial-access brokers. For NIS2-regulated operators running Zyxel SMB or branch firewalls, this is a P1 ticket ahead of anything else open — an unpatched appliance with a WAN-exposed management interface should be treated as compromised until forensically proven otherwise.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Upgrade firmware to ZLD V5.30 or later on every affected appliance: USG FLEX 50(W)/100(W)/200/500/700, USG20(W)-VPN, ATP series and VPN series. All versions 5.00 to 5.21 Patch 1 (4.60 to 5.21 Patch 1 for the VPN series) are vulnerable and exploitable without authentication over the HTTPS management port (TCP/443).
      • Block WAN-side reach to the web management interface (TCP/443, path /ztp/cgi-bin/handler) via firewall ACL until the firmware upgrade is confirmed. Move SSL-VPN to a non-standard port or temporarily fall back to IPsec.
      • Export the running config and diff for unauthorised admin accounts, injected SSH keys, altered firewall rules and modified ZTP/Cloud-CNM settings; revert anything unexpected.
      • Rotate all local, LDAP- and RADIUS-bound admin credentials, API keys and VPN pre-shared keys; invalidate active sessions (reboot after patching).
      • Hunt for on-device IoCs: inspect /tmp, /var/zyxel/ and cron jobs for foreign binaries, reverse shells (nc, bash -i) or tampered /etc files. If anything is found, isolate the device and treat it as compromised — factory-reset and rebuild from a known-good configuration, not from a backup of the possibly tampered device.

    2. Runbook step 2

      Mitigation layers

      • Network segmentation: expose the management interface only through a dedicated management VLAN or out-of-band path; restrict any remaining WAN-side HTTPS management via GeoIP ACL to admin jump hosts.
      • Upstream IPS/WAF rule (perimeter reverse proxy or inline IDS): block POST requests to /ztp/cgi-bin/handler containing the JSON parameters "mp_data_handler" or "setWanPortSt", especially when shell metacharacters (;, |, `, $() appear in the body.
      • Enable Suricata/Snort coverage for CVE-2022-30525 (ET 2036546 and vendor equivalents) and switch from alert to drop mode.
      • IAM hardening: enforce 2FA for all admin logins, rename the default admin account, set lockout to 3 failed attempts.
      • Forward syslog to an external SIEM — Zyxel logs locally to flash, which is the first thing wiped on compromise; off-box logging preserves forensic evidence.
      • Disable Cloud/Nebula/CNM management if not operationally required — the ZTP code path is the vulnerable surface.

    3. Runbook step 3

      Detection rules

      • Web/reverse-proxy logs: POST /ztp/cgi-bin/handler returning HTTP 200 or 500 without a preceding authenticated admin session. Sigma shape: selection: cs-method=POST AND cs-uri-stem="/ztp/cgi-bin/handler" AND sc-status in (200,500) — any external hit is a probable exploit attempt.
      • Perimeter NetFlow/Zeek: outbound sessions originating from the firewall management IP to internet hosts on ports 4444, 1337, 8080 or other known reverse-shell listeners — the firewall should never initiate client traffic to the internet.
      • Internal EDR/flow: new SSH or HTTP sessions sourced from the firewall interface into internal servers, indicating lateral movement from the perimeter inward.
      • Configuration drift (RANCID/Oxidized diff): unexpected admin account creation, new "allow any-any" rules, altered DNS or default-route settings between consecutive polls.
      • SIEM correlation KQL shape: WebLogs | where UrlPath contains "/ztp/cgi-bin/handler" | where RequestBody matches regex @"[;|\x60]|\$\(" — alerts on command-injection payload patterns.

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    Actively exploited: treat the vulnerability as a priority in vulnerability handling under Art. 21(2)(e) NIS2. If it is exploited in your environment, check the reporting obligation under Art. 23 (early warning within 24 hours).
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    Since 11.09.2026, manufacturers of affected products with digital elements must report actively exploited vulnerabilities under Art. 14 CRA, with an early warning within 24 hours via ENISA's single reporting platform.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    Description

    A OS command injection vulnerability in the CGI program of Zyxel USG FLEX 100(W) firmware versions 5.00 through 5.21 Patch 1, USG FLEX 200 firmware versions 5.00 through 5.21 Patch 1, USG FLEX 500 firmware versions 5.00 through 5.21 Patch 1, USG FLEX 700 firmware versions 5.00 through 5.21 Patch 1, USG FLEX 50(W) firmware versions 5.10 through 5.21 Patch 1, USG20(W)-VPN firmware versions 5.10 through 5.21 Patch 1, ATP series firmware versions 5.10 through 5.21 Patch 1, VPN series firmware versions 4.60 through 5.21 Patch 1, which could allow an attacker to modify specific files and then execute some OS commands on a vulnerable device.

    Source: NVD (NIST), cvelistv5, CISA KEV Catalog, CVE.org (MITRE)

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    ZyxelATP series firmware
    • 5.10 through 5.21 Patch 1
    • —
    ZyxelUSG 20(W)-VPN firmware
    • 5.10 through 5.21 Patch 1
    • —
    ZyxelUSG FLEX 100(W) firmware
    • 5.00 through 5.21 Patch 1
    • —
    ZyxelUSG FLEX 200 firmware
    • 5.00 through 5.21 Patch 1
    • —
    ZyxelUSG FLEX 50(W) firmware
    • 5.10 through 5.21 Patch 1
    • —
    ZyxelUSG FLEX 500 firmware
    • 5.00 through 5.21 Patch 1
    • —
    ZyxelUSG FLEX 700 firmware
    • 5.00 through 5.21 Patch 1
    • —
    ZyxelVPN series firmware
    • 4.60 through 5.21 Patch 1
    • —

    Vendors and products

    Affected operating systems

    Affected operating systems
    Otherzyxelatp100_firmware—
    Otherzyxelatp100w_firmware—
    Otherzyxelatp200_firmware—
    Otherzyxelatp500_firmware—
    Otherzyxelatp700_firmware—
    Otherzyxelatp800_firmware—
    Otherzyxelusg20w-vpn_firmware—
    Otherzyxelusg_flex_100w_firmware—
    Otherzyxelusg_flex_200_firmware—
    Otherzyxelusg_flex_500_firmware—
    Otherzyxelusg_flex_50w_firmware—
    Otherzyxelusg_flex_700_firmware—
    Otherzyxelvpn1000_firmware—
    Otherzyxelvpn100_firmware—
    Otherzyxelvpn300_firmware—
    Otherzyxelvpn50_firmware—

    Weakness classes (CWE)

    • CWE-78Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')

      Base

      The product constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command when it is sent to a downstream component.

      Entry at MITRE CWE-78

    Public exploit references

    Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.

    Public exploit references
    CISA KEV CatalogCISA Known Exploited Vulnerability (opens in a new tab)cisa.govactively exploited
    Packet StormZyxel Remote Command Execution (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—
    Packet StormZyxel Firewall ZTP Unauthenticated Command Injection (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—
    Packet StormZyxel USG FLEX 5.21 Command Injection (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—
    Packet StormZyxel Firewall SUID Binary Privilege Escalation (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—

    References & sources

    • zyxel.comsupport/Zyxel-security-advisory-for-OS-command-injection-vulner…x_refsource_CONFIRM, Vendor advisory
    • packetstormsecurity.comfiles/167176/Zyxel-Remote-Command-Execution.htmlx_refsource_MISC, Third-party advisory, Vulnerability database
    • packetstormsecurity.comfiles/167182/Zyxel-Firewall-ZTP-Unauthenticated-Command-Injecti…x_refsource_MISC, Exploit, Third-party advisory, Vulnerability database
    • packetstormsecurity.comfiles/167372/Zyxel-USG-FLEX-5.21-Command-Injection.htmlx_refsource_MISC, Exploit, Third-party advisory, Vulnerability database
    • packetstormsecurity.comfiles/168202/Zyxel-Firewall-SUID-Binary-Privilege-Escalation.ht…x_refsource_MISC, Exploit, Third-party advisory
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2022-30525government-resource, US government resource
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