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CVE-2026-65638 – Unauthenticated Remote Command Injection – ConfigServer Security & Firewall (CSF) 1

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Summary

CVE-2026-65638 is a critical OS command injection vulnerability in ConfigServer Security & Firewall (CSF) caused by improper escaping of a request URL. The flaw allows an unauthenticated remote attacker to execute arbitrary commands as the CSF service account, without requiring any credentials or user interaction. It carries a CVSS v4.0 base score of 9.2 (Critical).

Technical details

  • Root cause: CSF fails to properly escape a request URL before it is passed through to a shell command, resulting in a classic OS command injection (CWE-78).
  • Trigger conditions: An attacker sends a specially crafted request URL to a server running an affected CSF version; no authentication or prior access is required.
  • Attack vector: Network — the vulnerability is remotely exploitable over the network with low attack complexity.
  • Impact: Successful exploitation allows arbitrary command execution as the CSF service account, which can lead to full compromise of confidentiality, integrity, and availability of the affected host.

Affected software

  • WebPros ConfigServer Security & Firewall: versions 14.00 up to (but not including) 16.30
  • ConfigServer ConfigServer Security & Firewall: versions 14.00 and later (prior to the WebPros fix)

Severity

  • CVSS v4.0 Base Score: 9.2 (Critical)
  • Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:L/SI:L/SA:N

Mitigation and recommended actions

  • Immediate: Upgrade ConfigServer Security & Firewall to version 16.30 or later, where the improper URL escaping has been fixed.
  • If patching is not immediately possible: Restrict or firewall off remote access to the CSF-managed service/interface exposed to the network until the upgrade can be applied, and monitor logs for anomalous requests containing shell metacharacters in URLs.

References

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