CVE-2026-67402: Critical RCE in ConfigServer Firewall — Update CSF to 16.31 Now
If your server runs cPanel with ConfigServer Firewall (CSF), drop what you’re doing and check your CSF version. On September 3, 2026, cPanel pushed a critical patch for CVE-2026-67402 — a remote code execution vulnerability in CSF’s Messenger service that lets an unauthenticated attacker run arbitrary commands as the Apache user. That’s a bad sentence to read about a piece of software whose entire job is to protect your server. What Is CSF, and Why Did cPanel Inherit It? ConfigServer Security & Firewall has been a staple of cPanel/WHM setups for years — it’s the iptables-based firewall layer that handles port blocking, login failure detection, and email alerts. The original developer discontinued it on August 31, 2025 and released the code as open-source under GPLv3. cPanel (now WebPros) stepped in on February 25, 2026 and forked it, taking over security maintenance. ...