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CVE-2026-78211 – Unauthenticated OS Command Injection (RCE) – 4MOSAn GCB Doctor < 20260621

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Summary

CVE-2026-78211 is a critical, unauthenticated OS command injection vulnerability in 4MOSAn GCB Doctor, a Taiwanese Government Configuration Baseline (GCB) compliance and vulnerability-scanning product developed by 4MOSAn Security Technology. The flaw resides in a leftover ADOdb test page that fails to sanitize a request parameter, allowing a remote, unauthenticated attacker to inject and execute arbitrary OS commands on the underlying server. The issue carries a CVSS v3.1 base score of 9.8 (Critical).

Technical details

  • Root cause: An ADOdb test/debug page shipped with 4MOSAn GCB Doctor was not removed from production builds. This page accepts a parameter that is passed unsanitized into a system command execution routine (CWE-78: OS Command Injection).
  • Trigger conditions: An attacker only needs network access to the exposed GCB Doctor web interface; no authentication, user interaction, or special privileges are required to reach the vulnerable endpoint.
  • Attack vector: Network (remote), low attack complexity — the attacker sends a crafted request with malicious shell metacharacters/commands in the vulnerable parameter of the ADOdb test page.
  • Impact: Successful exploitation results in arbitrary command execution with the privileges of the web service process, enabling full compromise of confidentiality, integrity, and availability of the host — including the underlying FreeBSD-based GCB management center.
  • Discovery/credit: Reported by security researcher Linwz (DEVCORE) via Taiwan’s TWCERT/CC coordinated disclosure process, with an advisory published August 24, 2026.

Affected software

  • 4MOSAn GCB Doctor — all versions prior to 20260621

Severity

  • CVSS v3.1 Base Score: 9.8 (Critical)
  • Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Mitigation and recommended actions

  • Immediate: Upgrade 4MOSAn GCB Doctor to version 20260621 or later, and apply the accompanying FreeBSD-based GCB Management Center security upgrade as specified by the vendor.
  • If immediate patching is not possible:
    • Restrict network access to the GCB Doctor management interface to trusted internal hosts/VPN only; do not expose it directly to the internet.
    • Disable or remove any ADOdb test/debug pages or endpoints if identifiable on the deployed instance.
    • Monitor web server and application logs for unexpected requests to ADOdb-related paths and for anomalous child-process/command execution originating from the web service account.
    • Apply network segmentation and firewall rules to limit inbound access to the affected product until the patch can be applied.

References

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