Description

GetSimple CMS is a content management system (CMS), and GetSimple CMS CE is the community edition of that CMS. A logic flaw in GetSimple CMS (v3.4.0a and below) and GetSimpleCMS-CE (v3.3.22 and below) allows unauthenticated attackers to create a new administrator account. The application features an automated security control designed to delete the sensitive `admin/setup.php` file post-installation. However, this control is neutralized by a self-exclusion bug within the deletion logic, leaving the setup script accessible for unauthorized account creation even after a legitimate installation is completed. As of time of publication, no known patched versions are available.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "9.8",
  "pubDate": "2026-09-11T20:17:14.060Z",
  "pubdate": "2026-09-11T20:17:14.060Z",
  "executiveSummary": "A critical logic flaw exists in GetSimple CMS (v3.4.0a and below) and GetSimpleCMS-CE (v3.3.22 and below) that enables unauthenticated remote attackers to create a new administrator account.\nThe vulnerability originates from a failure in the automated post-installation security mechanism intended to remove the sensitive 'admin/setup.php' file.\nDue to a self-exclusion bug within the file deletion logic, the installation script remains accessible on the web server after a successful initial deployment.\nThis allows any remote attacker to re-trigger the setup process, effectively overriding or creating a new administrative user without requiring pre-existing authentication.\nThe impact is total system compromise, as unauthorized administrative access grants an attacker full control over the CMS, including the ability to execute arbitrary code, modify site content, and access sensitive data.\nGiven that no official patches are currently available, the risk to affected systems is severe, requiring immediate manual administrative intervention to mitigate exposure.",
  "technicalDetails": "The root cause of this vulnerability is an improper implementation of file management logic within the GetSimple CMS and GetSimpleCMS-CE installation process. During the standard setup procedure, the application is designed to trigger a routine that deletes the 'admin/setup.php' file to prevent post-installation re-initialization.\nHowever, a self-exclusion bug within this deletion function prevents the script from effectively removing itself from the server's filesystem upon completion of the configuration. Consequently, the installation endpoint remains active and reachable via standard HTTP GET/POST requests.\nThe exploitation flow is straightforward and does not require elevated privileges or authentication. An attacker can navigate to the 'admin/setup.php' URL on an already-installed instance of the CMS. Because the script remains present, the application processes the request as if it were a fresh installation.\nBy interacting with the reachable 'admin/setup.php' script, an unauthenticated attacker can supply new administrative credentials. The script performs the database write operation necessary to create the new account, overriding existing settings or appending the new user to the authorized administrative list.\nOnce the attacker successfully executes this process, the resulting session provides full administrative control over the CMS dashboard. The vulnerability represents an 'Insecure Default/Configuration' issue, categorized as a failure to properly decommission setup components.\nThe attack is remotely exploitable and does not require complex payloads; it simply necessitates access to the publicly available 'admin/setup.php' file. Post-exploitation, an attacker gains complete control over the site configuration, plugin uploads, and theme modifications, facilitating arbitrary code execution (ACE) through the administrative interface's file management capabilities. The vulnerability remains present as long as the 'admin/setup.php' file is detected by the server and accessible via the web root."
}