fearlessgeekmedia FearlessCMS up to 0.1.3a Updater updater-handler.php perform_update backdoor

Summaryinfo

A vulnerability, which was classified as problematic, has been found in fearlessgeekmedia FearlessCMS up to 0.1.3a. The affected element is the function perform_update of the file admin/updater-handler.php of the component Updater. This manipulation causes backdoor. This vulnerability is registered as CVE-2026-55695. Remote exploitation of the attack is possible. No exploit is available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability has been found in fearlessgeekmedia FearlessCMS up to 0.1.3a and classified as problematic. Affected by this vulnerability is the function perform_update of the file admin/updater-handler.php of the component Updater. The manipulation with an unknown input leads to a backdoor vulnerability. The CWE definition for the vulnerability is CWE-912. The product contains functionality that is not documented, not part of the specification, and not accessible through an interface or command sequence that is obvious to the product's users or administrators. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

FearlessCMS is a flat-file content management system centered on simplicity and open source. In 0.1.2b and earlier, an authenticated administrator can set an arbitrary Git repository URL through admin/updater-handler.php and trigger perform_update, which passes the URL to update.sh. The updater clones the repository and replaces the live plugins/, admin/, and includes/ directories without verifying the repository's identity, signatures, or contents. Because router.php permits existing PHP files under plugins to be executed by the PHP development server, attacker-supplied update content can execute arbitrary PHP with the web server process's privileges and persist as a backdoor. This issue is fixed in version 0.1.3b.

It is possible to read the advisory at github.com. This vulnerability is known as CVE-2026-55695 since 06/17/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation requires an enhanced level of successful authentication. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1588.001 according to MITRE ATT&CK.

By approaching the search of inurl:admin/updater-handler.php it is possible to find vulnerable targets with Google Hacking.

Upgrading to version 0.1.3b eliminates this vulnerability.

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Productinfo

Vendor

• fearlessgeekmedia

Name

• FearlessCMS

Version

• 0.1.3a

Website

• Product: https://github.com/fearlessgeekmedia/FearlessCMS/

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