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cPanel ConfigServer Security & Firewall Vulnerability Allows Remote Attacker to Execute Arbitrary Commands

CSF 14.00–16.29 (CVE-2026-65638) lets unauthenticated attackers execute arbitrary commands via the MESSENGER service on cPanel/WHM servers; version 16.30 fixes it.

CVE-2026-65638 affects ConfigServer Security & Firewall (CSF) versions 14.00 through 16.29 and allows unauthenticated remote attackers to execute arbitrary commands through the MESSENGER service, running under the unprivileged CSF service account rather than root. Exploitation requires the non-default MESSENGER service to be enabled and a reCAPTCHA secret configured, reducing exposure for standard deployments. CSF 16.30 and later fix the flaw; administrators who cannot update immediately can set MESSENGER = 0 in /etc/csf/csf.conf as a temporary mitigation.

cPanel Urges Users to Patch ConfigServer Firewall Remote Code Execution Flaw

cPanel urges administrators to patch CVE-2026-65638, a flaw letting unauthenticated attackers run commands through ConfigServer Firewall's MESSENGER service; update to CSF 16.30.

CVE-2026-65638 in ConfigServer Security & Firewall (CSF) 14.00–16.29 allows unauthenticated remote attackers to execute arbitrary commands via the MESSENGER service, which is exposed only when MESSENGER is enabled and a reCAPTCHA secret has been configured. Exploitation yields command execution under the unprivileged CSF service account, providing a foothold for reconnaissance, data access, or lateral movement on internet-facing cPanel/WHM hosting infrastructure. CSF 16.30 or later fixes the issue; disabling MESSENGER in /etc/csf/csf.conf and restarting csf and lfd is a temporary mitigation.

Related CVEs

  • Unauthenticated shell command injection in ConfigServer Security & Firewall (CSF)
    CVE-2026-65638 is an unauthenticated shell command injection flaw (CWE-78) in ConfigServer Security & Firewall (CSF), caused by improper escaping of a request URL. An attacker who sends a crafted request URL containing shell metacharacters to the affected web-facing component can have arbitrary commands executed under the CSF service account. Successful exploitation therefore yields command execution on the server in the context of the CSF service account, with a critical CVSS 4.0 score of 9.2 reflecting high confidentiality, integrity, and availability impact on the vulnerable system. The flaw affects versions originally distributed by ConfigServer as well as versions of the WebPros-maintained fork that contain the vulnerable code; WebPros has fixed it in version 16.30, and other independently maintained CSF forks should be evaluated separately. There is no public proof of concept, the issue is not in CISA's Known Exploited Vulnerabilities catalog, and no exploitation has been reported to date.
    · ConfigServer Security & Firewall (CSF) · WebPros ConfigServer Security & Firewall (WebPros-maintained fork) Versions containing the vulnerable code; fixed in version 16.30mass

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