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Actively exploited

CVE-2017-18368 Zyxel P660HN-T1A Routers Command Injection Vulnerability

Zyxel P660HN-T1A routers contain a command injection vulnerability in the Remote System Log forwarding function, which is accessible by an unauthenticated user and exploited via the remote_host parameter of the ViewLog.asp page.

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

Our Assessment

Should You Worry?

Patch nowCybergen assessment
  • CISA confirmed exploitation in the wild and added it to the Known Exploited Vulnerabilities catalogue on 7 Aug 2023.
  • Rated Critical severity (CVSS 9.8, scored by CISA).
  • It has been in the catalogue for 1,187 days. Systems still unpatched now have almost certainly been scanned for it.
The Vulnerability

What It Is

The ZyXEL P660HN-T1A v1 TCLinux Fw $7.3.15.0 v001 / 3.40(ULM.0)b31 router distributed by TrueOnline has a command injection vulnerability in the Remote System Log forwarding function, which is accessible by an unauthenticated user. The vulnerability is in the ViewLog.asp page and can be exploited through the remote_host parameter.

From Watch to Action

What To Do Now

  1. 1

    Find it

    Search your asset inventory and external attack surface for Zyxel P660HN-T1A Routers. Include cloud images, appliances and anything a supplier runs for you.

    Attack Surface Management
  2. 2

    Fix it

    Apply mitigations per vendor instructions or discontinue use of the product if mitigations are 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 critical, 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 28 Aug 2023 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

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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-2024-40890Zyxel 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-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-2017-18368 and every other exploited flaw on the list.

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Evidence

Sources

  1. CISA Known Exploited Vulnerabilities catalogue
  2. NVD: CVE-2017-18368
  3. CVE record: CVE-2017-18368
  4. FIRST EPSS
  5. zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-a-new-variant-of-gafgyt-
  6. zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-command-injection-vulner
  7. seclists.org/fulldisclosure/2017/Jan/40
  8. ssd-disclosure.com/index.php/archives/2910
  9. unit42.paloaltonetworks.com/new-mirai-variant-targets-enterprise-wireless-presentation-display-syste
  10. raw.githubusercontent.com/pedrib/PoC/master/advisories/zyxel_trueonline.txt
  11. zyxel.com/support/announcement_unauthenticated.shtml