502 Bad Gateway error on Plesk when using Comodo ModSecurity ruleset

[Suhitha]

Symptoms

• All websites show a 502 Bad Gateway error
• Switching to the Atomic Standard ruleset resolves the problem
• The Plesk UI shows the following error message:

      AH00526: Syntax error on line 6035 of /etc/httpd/conf/modsecurity.d/rules/comodo_free/30_Apps_OtherApps.conf: Error creating rule: Error compiling pattern (offset 4): invalid range in character class       

Cause

The mod_security package installed from the Atomic repository is not fully compatible with the current Comodo rule set.

Resolution

• Connect to the Plesk server via SSH.
• Execute the command to replace the ModSecurity package with the version provided by Plesk:

# dnf swap mod_security mod_security --enablerepo=PLESK_18_0_70-extras --disablerepo=atomic --skip-broken