Security Advisory: CSF Firewall Port Rule Race Condition

Under heavy connection churn, CSF may briefly drop an active port rule before the reload completes, exposing SSH briefly on default configurations.

Low 2026-06-25

CSF AlmaLinux 8 AlmaLinux 9 CentOS 7 CloudLinux 7 CloudLinux 8 CloudLinux 9

Affected Versions

CSF 14.20 and earlier

Patched Version

CSF 14.21

Default Update CMD

yum update -y

Fix Commands

AlmaLinux 9 / CloudLinux 9

cd /etc/csf
csf -u
csf -r

cd /etc/csf
csf -u
csf -r

cd /etc/csf
csf -u
csf -r

References

Security Advisories

Security: Privilege Escalation via Phusion Passenger’s Watchdog API

2026-09-08

Security: CVE-2026-41940 – cPanel & WHM / WP2 Security Update 04/28/2026

2026-09-08

Security: CSF Security Release – September 3rd, 2026

2026-09-08

Select your product and operating system to see the exact fix commands that apply to you.