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OpenAdvisories
Medium · 5.5 CVE-2026-54611 EUVD-2026-73561

InstantCMS has Remote Code Execution in package installer

Published Sep 8, 2026 · Updated Sep 9, 2026 · Assigned by GitHub_M

Description

InstantCMS is a free and open source content management system. Versions prior to 2.18.2 have a Remote Code Execution (RCE) issue that allows remote authenticated attackers to execute any PHP code via the component installer. It is possible to upload a malicious component into the server, however, it won't be installed, but upload files will be executed. Normally all php files in upload folder are not executed, however, by uploading custom .htaccess it becomes possible. Version 2.18.2 contains a fix.

Affected products

VendorProductAffectedFixed
instantsoft icms2 < 2.18.2 —

References