CVE-2026-66747: Software Security Vulnerability Vulnerability

CRITICAL
Advisory Identifier: GHSA-gf5q-q6h6-j87v
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CVSS 9.8
CWE-506
Published
Advisory Summary

CVE-2026-66747 is a CRITICAL (CVSS 9.8) security vulnerability vulnerability (CWE-506: Embedded Malicious Code) affecting Software libraries in the Maven ecosystem. The weakness occurs when the product contains code that appears to be malicious in nature.. Remediation is available in the latest vendor maintenance releases.

CVE-2026-66747 at a Glance

CVE Identifier CVE-2026-66747
GHSA Identifier GHSA-gf5q-q6h6-j87v
Severity CRITICAL
CVSS v3.1 Base Score 9.8
CWE Classification CWE-506: Embedded Malicious Code
Affected Product Software
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 9.8

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality High (C:H)
Integrity High (I:H)
Availability High (A:H)

How to Fix CVE-2026-66747

To remediate this vulnerability, upgrade all affected Software dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

mvn dependency:tree

How to Check if You Are Affected

To determine whether your Java application is affected by CVE-2026-66747, inspect your build dependencies using the Maven Dependency Plugin:

mvn dependency:tree

Analyze the terminal output to locate any version of Software in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than the patched release), your application is affected.

Note: The mvn dependency:tree command inspects the resolved dependency graph declared in your project's POM files; it does not perform automated security scanning or inspect runtime dynamic classpaths. Always verify runtime container classpaths and shaded JARs.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-506: Embedded Malicious Code, where the product contains code that appears to be malicious in nature. In Software, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

Zbtlink router firmware ships an embedded remote-control implant, ENDLESSDOORS, present in every published build across the product line. It is the open-source ycsunjane/rctl tool built in as an OpenWrt package (librctl.so), started at boot and run as root under the process name kworker to blend in with the kernel's [kworker/*] threads. It opens no listening port; it phones home over cleartext TCP to a hardcoded command-and-control server (command channel 7000, interactive-shell callback 7001) with no authentication and no transport encryption, re-attempting contact roughly every 35 seconds. Its command handler passes any received string to popen() as uid=0, and a reserved rctlbash command returns an interactive root shell. Because the channel is unauthenticated and cleartext, control is not limited to whoever planted it: any party that answers at the C2 address, occupies the network path (DNS or route hijack), or acquires the hardcoded fallback domain obtains unauthenticated remote code execution as root.

References

NVD — CVE-2026-66747 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-66747
Software Source Repository REPOSITORY
https://github.com/ycsunjane/rctl
www.vulncheck.com/advisories/zbt-endl... WEB
https://www.vulncheck.com/advisories/zbt-endlessdoors
www.vulncheck.com/blog/zbt-endlessdoo... WEB
https://www.vulncheck.com/blog/zbt-endlessdoors
www.zbtlink.com/pages/zbt-router-fi... WEB
https://www.zbtlink.com/pages/zbt-router-firmware-download

Frequently Asked Questions

What is CVE-2026-66747?
CVE-2026-66747 is a security vulnerability in Software classified as a security vulnerability vulnerability under CWE-506: Embedded Malicious Code.
Which Software versions are affected?
Affected versions include releases prior to current release patches.
What version fixes CVE-2026-66747?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
What is the CVSS score of CVE-2026-66747?
CVE-2026-66747 has a CVSS v3.1 base score of 9.8 (CRITICAL) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2026-66747?
CVE-2026-66747 is classified under CWE-506: Embedded Malicious Code (The product contains code that appears to be malicious in nature.).
How can I check Maven dependencies for CVE-2026-66747?
Run the dependency tree command: 'mvn dependency:tree'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-gf5q-q6h6-j87v",
  "modified" : "2026-08-05T12:31:30Z",
  "published" : "2026-08-05T12:31:30Z",
  "aliases" : [ "CVE-2026-66747" ],
  "details" : "Zbtlink router firmware ships an embedded remote-control implant, ENDLESSDOORS, present in every published build across the product line. It is the open-source ycsunjane/rctl tool built in as an OpenWrt package (librctl.so), started at boot and run as root under the process name kworker to blend in with the kernel's [kworker/*] threads. It opens no listening port; it phones home over cleartext TCP to a hardcoded command-and-control server (command channel 7000, interactive-shell callback 7001) with no authentication and no transport encryption, re-attempting contact roughly every 35 seconds. Its command handler passes any received string to popen() as uid=0, and a reserved rctlbash command returns an interactive root shell. Because the channel is unauthenticated and cleartext, control is not limited to whoever planted it: any party that answers at the C2 address, occupies the network path (DNS or route hijack), or acquires the hardcoded fallback domain obtains unauthenticated remote code execution as root.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X"
  } ],
  "affected" : [ ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-66747"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/ycsunjane/rctl"
  }, {
    "type" : "WEB",
    "url" : "https://www.vulncheck.com/advisories/zbt-endlessdoors"
  }, {
    "type" : "WEB",
    "url" : "https://www.vulncheck.com/blog/zbt-endlessdoors"
  }, {
    "type" : "WEB",
    "url" : "https://www.zbtlink.com/pages/zbt-router-firmware-download"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-506" ],
    "severity" : "CRITICAL",
    "github_reviewed" : false,
    "github_reviewed_at" : null,
    "nvd_published_at" : "2026-08-05T11:16:25Z"
  }
}