CVE-2026-56662 in GetSimple CMS
Summary
by MITRE • 10/01/2026
GetSimple CMS is a content management system (CMS), and GetSimple CMS CE is the community edition of that CMS. Prior to version 1.5, the UpdateCE update form contained no anti-CSRF token, and the POST handler performed no token or request-origin verification. A remote attacker can host a page that auto-submits a forged POST to the update endpoint; when an authenticated administrator visits it, the server performs an attacker-directed download-and-deploy operation in the administrator's session — with no further interaction. Because the deployed content is executed (see the related ZIP-extraction advisory), this yields remote code execution. The url field is additionally written into the form unescaped, providing a secondary HTML-injection sink via a malicious upgrade.json. This issue has been patched in version 1.5.
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Analysis
by VulDB Data Team • 10/01/2026
The vulnerability identified in GetSimple CMS prior to version 1.5 represents a critical failure in session management and input validation that allows for remote code execution through cross-site request forgery mechanisms. The core technical flaw resides within the UpdateCE update form, which lacks any implementation of anti-CSRF tokens or request-origin verification checks in its POST handler. In standard web application security practices, state-changing operations such as software updates must require a unique, unpredictable token that is tied to the user's session and validated by the server before processing the request. The absence of this control means that an attacker can craft a malicious webpage containing a script designed to automatically submit a forged POST request to the vulnerable update endpoint. When an authenticated administrator with sufficient privileges visits this malicious page, their browser will execute the submission using their active session cookies without any further interaction or user consent.
This lack of verification enables a remote attacker to force the CMS into performing a download-and-deploy operation under the context of the victim's administrative account. The operational impact is severe because the deployed content is not merely stored but actively executed by the system. This execution capability transforms what might otherwise be a simple defacement or data manipulation issue into a full remote code execution vulnerability. By leveraging this mechanism, an attacker can inject and run arbitrary server-side scripts, gaining complete control over the underlying web application environment. This level of access typically allows for further lateral movement within the network, theft of sensitive data stored by the CMS, and potential compromise of other systems connected to or accessible from the compromised host.
Additionally, the vulnerability includes a secondary vector involving HTML injection due to improper output encoding. The url field is written into the form unescaped, creating an opportunity for cross-site scripting if a malicious upgrade.json file is utilized during the update process. While this specific aspect contributes to the overall risk profile by potentially allowing session hijacking or phishing attacks through injected scripts, it operates in conjunction with the primary CSRF flaw to facilitate the broader attack chain leading to code execution. The combination of these flaws highlights significant deficiencies in both request validation and output encoding within the affected versions of GetSimple CMS CE.
From a classification perspective, this vulnerability aligns with CWE-352, which describes Cross-Site Request Forgery (CSRF), due to the lack of anti-CSRF tokens and origin verification. The exploitation technique also maps to MITRE ATT&CK tactic T1078, specifically valid accounts, as it relies on hijacking an authenticated administrator's session. Furthermore, the execution of deployed content relates to CWE-94, Improper Control of Generation of Code (Code Injection), and potentially CWE-20, Improper Input Validation, given the unescaped url field. The successful exploitation allows for unauthorized code execution, which is a critical security breach in any content management system handling administrative functions.
To mitigate this vulnerability, organizations running GetSimple CMS must immediately upgrade to version 1.5 or later, where these issues have been patched. For systems that cannot be updated instantly due to operational constraints, implementing reverse proxy rules to validate request origins and enforce strict Content Security Policy headers can provide some level of protection against CSRF attacks. Additionally, ensuring that all user-supplied input is properly encoded before being written into HTML output will mitigate the secondary HTML injection risk. Regular security audits focusing on session management practices and input validation are essential for maintaining the integrity of web applications susceptible to such flaws.