Cannot install update on Plesk for Windows: The installation of the package 'plesk-modsecurity-module' failed with code 1603

Vladimir Levchuk

Updated August 21, 2026 12:27

Plesk for Windows kb: technical Plesk Obsidian for Windows

Symptoms

Plesk update installation fails:

PLESK_ERROR: Error: The installation of the package 'plesk-modsecurity-module' failed with code 1603. (upgrade: Upgrading ModSecurity IIS Module...)

Cause

Windows msiexec failed to update ModSecurity IIS module. Code 1603 is generic error, and issue could be caused by various reasons (which might be logged in Plesk autoinstaller3.log file).

Resolution

Reinstall ModSecurity from scratch after installing Plesk update.

Reinstall ModSecurity:

Connect to the server via RDP
Open cmd.exe and remove ModSecurity modules from IIS:

C:\> %windir%\system32\inetsrv\appcmd.exe uninstall module "ModSecurity IIS (32bits)"
Uninstalled MODULE "ModSecurity IIS (32bits)"

C:\> %windir%\system32\inetsrv\appcmd.exe uninstall module "ModSecurity IIS (64bits)"
Uninstalled MODULE "ModSecurity IIS (64bits)"
Restart IIS:

C:\> iisreset
Remove ModSecurity component from Plesk:

C:\> plesk installer --select-release-current --remove-component modsecurity
Install Plesk update:

C:\> plesk installer update
Install ModSecurity component:

C:\> plesk installer --select-release-current --install-component modsecurity