+44 1865 950 828 Secure Your Business
Actively exploited

CVE-2024-40890 Zyxel DSL CPE OS Command Injection Vulnerability

Multiple Zyxel DSL CPE devices contain a post-authentication command injection vulnerability in the CGI program that could allow an authenticated attacker to execute OS commands via a crafted HTTP request.

From the CISA KEV catalogue version 2026.11.06, with Cybergen analysis. Updated 6 Nov 2026.

Our Assessment

Should You Worry?

Patch urgentlyCybergen assessment
  • CISA confirmed exploitation in the wild and added it to the Known Exploited Vulnerabilities catalogue on 11 Feb 2025.
  • Rated High severity (CVSS 8.8, scored by Vendor).
  • It has been in the catalogue for 633 days. Systems still unpatched now have almost certainly been scanned for it.
The Vulnerability

What It Is

**UNSUPPORTED WHEN ASSIGNED** A post-authentication command injection vulnerability in the CGI program of the legacy DSL CPE Zyxel VMG4325-B10A firmware version 1.00(AAFR.4)C0_20170615 could allow an authenticated attacker to execute operating system (OS) commands on an affected device by sending a crafted HTTP POST request.

Affected Versions

ProductVersions
Zyxel VMG4325-B10A firmware<= 1.00(AAFR.4)C0_20170615

From the public CVE record, as supplied by the vendor. Always confirm against the vendor advisory.

From Watch to Action

What To Do Now

  1. 1

    Find it

    Search your asset inventory and external attack surface for Zyxel DSL CPE Devices. Include cloud images, appliances and anything a supplier runs for you.

    Attack Surface Management
  2. 2

    Fix it

    The impacted product could be end-of-life (EoL) and/or end-of-service (EoS). Users should discontinue product utilization if a current mitigation is unavailable.

    Vulnerability Management
  3. 3

    Hunt for compromise

    If an affected system was reachable before you patched, assume it may have been hit. Check logs, new accounts, web shells and outbound connections from the date of exposure.

    Incident Response
  4. 4

    Prove it is fixed

    Rescan or test the system after patching. Upgrades that fail silently and forgotten secondary instances are common.

    Penetration Testing

Vendor Advisories

Regulation

The Compliance Clock

Cyber EssentialsRated high, so if it affects devices in your Cyber Essentials scope, the update must be installed within 14 days of the vendor releasing it.NIS2If exploitation causes a significant incident, essential and important entities owe their CSIRT an early warning within 24 hours and a notification within 72 hours.DORAFinancial entities must classify ICT incidents and send an initial notification for a major incident within strict deadlines, with exploited flaws a common cause.US federal (BOD 22-01)Federal civilian agencies had until 4 Mar 2025 to remediate. A sensible benchmark for everyone else.

General guidance, not legal advice. Your obligations depend on your sector, scope and jurisdiction.

Stay Ahead

More Exploited Zyxel Flaws

Get alerts for ZyxelWe email you when a new Zyxel vulnerability is confirmed as exploited. Add more vendors on Threat Watch.

By signing up you agree to receive Threat Watch alerts. Unsubscribe at any time. See our Privacy Policy.

CVE-2026-7273Zyxel GS1900 Series Switches Stack-Based Buffer Overflow VulnerabilityAdded 21 Sep 2026CVE-2024-40891Zyxel DSL CPE OS Command Injection VulnerabilityAdded 11 Feb 2025CVE-2024-11667 · RansomwareZyxel Multiple Firewalls Path Traversal VulnerabilityAdded 3 Dec 2024CVE-2017-6884 · RansomwareZyxel EMG2926 Routers Command Injection VulnerabilityAdded 18 Sep 2023CVE-2017-18368Zyxel P660HN-T1A Routers Command Injection VulnerabilityAdded 7 Aug 2023CVE-2023-27992Zyxel Multiple NAS Devices Command Injection VulnerabilityAdded 23 Jun 2023

All 13 exploited Zyxel vulnerabilities

Not Sure If You Are Exposed?

Our attack surface and vulnerability teams can check your internet-facing estate for CVE-2024-40890 and every other exploited flaw on the list.

Check My Exposure
Evidence

Sources

  1. CISA Known Exploited Vulnerabilities catalogue
  2. NVD: CVE-2024-40890
  3. CVE record: CVE-2024-40890
  4. FIRST EPSS
  5. zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-command-injection-and-in
  6. zyxel.com/service-provider/global/en/security-advisories/zyxel-security-advisory-command-injection-i