Zyxel P660HN-T1A Routers Command Injection Vulnerability (CVE-2017-18368)
Published In CISA KEV since Sources: CVE.org
What is affected, what to do
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.
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
- Billion 5200W-T Firmware
eq 7.3.8.0..7.3.8.0 - Zyxel P660HN-T1A V2 Firmware
eq 7.3.15.0..7.3.15.0 - Zyxel P660HN-T1A V1 Firmware
eq 7.3.15.0..7.3.15.0
- Billion 5200W-T Firmware
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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
94.5 %
EPSS score
High — model estimates ≥ 50% chance of real-world exploitation within 30 days.
Source: FIRST EPSS, percentile 99.85
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- 228.76 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- 94.5 %
- 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- 99.85
- 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 4 February 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 of years of mass exploitation by Mirai and Gafgyt botnet variants that embed this exact parameter in their recruitment scripts — unauthenticated, network-reachable, trivial payload, among the CVEs most likely to be exploited. The target profile is ISP-distributed consumer CPE that leaks into enterprise estates as home-office or branch routers and rarely appears in central asset management. For NIS2-regulated organisations, every exposed unit must be treated as a perimeter breach point until isolation or replacement is proven. Priority is urgent and blocking even without the ransomware flag, since botnet enlistment carries DDoS co-liability and reputational exposure.
Runbook step 1
Immediate response (0-24 h)
- Inventory every Zyxel P660HN-T1A (v1 and v2, firmware 7.3.15.0) and Billion 5200W-T (firmware 7.3.8.0) in the estate, including TrueOnline-shipped units, home-office routers and remote-site CPE. Cross-check your public ASN ranges in Shodan/Censys.
- Remove the device's web management interface (TCP/80, TCP/443, TCP/8080 if enabled) from the public internet. Enforce the ACL upstream or at the ISP — the CPE itself has no reliable WAN-side ACL covering ViewLog.asp.
- Disable Remote System Log forwarding in the web UI (Maintenance → Logs → Remote Log Settings); this is the exact feature that parses the vulnerable remote_host parameter.
- Confirm with the vendor: no official fix exists for the affected firmware — the hardware is end-of-life. Initiate replacement with supported CPE (vendor-managed or OpenWrt-capable) and treat the Zyxel/Billion units as a decommissioning backlog.
- Rotate admin credentials and inspect every potentially exposed unit for persistence (unknown cron entries, modified /etc/passwd, rogue processes, altered WAN DNS). On any suspicion, factory-reset, re-flash firmware offline, reconfigure from a clean baseline.
Runbook step 2
Mitigation layers
- Network segmentation: place affected CPE in an isolated VLAN with egress limited to essential services (internal DNS resolvers, NTP, management VPN). Deny any lateral path into production or OT networks.
- Perimeter filtering: at the upstream gateway or carrier firewall, drop inbound requests to
/ViewLog.aspand any POST body containing theremote_hostparameter. WAF rule: block HTTP requests whose URI matchesViewLog.aspand whose query or body contains shell metacharacters (;,|,`,$(,&&). - IPS signature: Snort/Suricata rule on HTTP content
remote_host=combined with URL-encoded shell operators (%3B, %7C, %60). Enable the public ET Open signatures for CVE-2017-18368 (Mirai/Gafgyt variants). - Egress filtering: block outbound connections from CPE on classic Mirai C2 ports (TCP/23, TCP/48101, TCP/5555) and alert on outbound traffic to known botnet infrastructure ranges.
- DNS hygiene: force the CPE's WAN DNS to enterprise-controlled resolvers and monitor configuration drift via SNMP polling or baseline diffing — Mirai-class malware frequently rewrites resolver settings.
- Long-term fix: formally sunset this EoL device class via change management and update procurement policy to NIS2 supply-chain and support-lifecycle requirements.
Runbook step 3
Detection rules
- Inspect web-server and reverse-proxy logs for GET or POST requests to
/ViewLog.aspcarrying aremote_hostparameter. Sigma shape:selection: cs-uri-stem endswith '/ViewLog.asp' AND cs-uri-query contains 'remote_host='combined with a shell-metacharacter match. - Zeek/Suricata http.log: alert on
http.uri contains "ViewLog.asp"ANDhttp.request.bodymatchesremote_host=.*[;|&$]`. Retro-hunt historical logs — these devices were often exposed and unmonitored for years. - Netflow/IPFIX: unusual outbound traffic from CPE IPs to TCP/23 (Telnet) or periodic beaconing to single foreign IPs — a classic Mirai recruitment signal.
- SIEM correlation (KQL shape):
WebLogs | where UrlPath has "ViewLog.asp" and UrlQuery has "remote_host" | where UrlQuery matches regex @"[;|&\x60$()]"as a hunting query across all perimeter log sources. - Configuration drift: daily SNMP/SSH baseline of CPE configuration; alert on any change to syslog destinations, DNS servers or admin accounts without a matching change ticket.
- Inspect web-server and reverse-proxy logs for GET or POST requests to
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
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.
Source: NVD (NIST), cvelistv5, CISA KEV Catalog, CVE.org (MITRE)
Vendors and products
Affected operating systems
| Other | billion | 5200w-t_firmware | 7.3.8.0 |
| Other | zyxel | p660hn-t1a_v1_firmware | 7.3.15.0 |
| Other | zyxel | p660hn-t1a_v2_firmware | 7.3.15.0 |
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.
| CISA KEV Catalog | CISA Known Exploited Vulnerability (opens in a new tab)cisa.gov | actively exploited | |
| Reference tagged as exploit | seclists.org (opens in a new tab) | PoC (publicly reported)reported, not verified | — |
References & sources
- seclists.orgfulldisclosure/2017/Jan/40x_refsource_MISC, Exploit, Mailing list, Third-party advisory
- ssd-disclosure.comindex.php/archives/2910x_refsource_MISC, Exploit, Technical description, Third-party advisory
- unit42.paloaltonetworks.comnew-mirai-variant-targets-enterprise-wireless-presentation-disp…x_refsource_MISC, Technical description, Third-party advisory
- raw.githubusercontent.compedrib/PoC/master/advisories/zyxel_trueonline.txtx_refsource_MISC, Exploit, Third-party advisory
- zyxel.comsupport/announcement_unauthenticated.shtmlx_refsource_MISC, Broken link
- cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2017-18368government-resource, US government resource
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<a href="https://intel.neosec.eu/en/cve/CVE-2017-18368"><img src="https://intel.neosec.eu/badge/cve/CVE-2017-18368.svg?lang=en" alt="CVE-2017-18368 – NEOSEC Intel" height="20"></a>