CVE-2026-56660 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 update handler in UpdateCE.php downloads a ZIP archive and extracts its contents into the web root without validating file types or extraction paths. Because PHP files are written into a web-accessible directory, an attacker who can cause a malicious archive to be processed achieves remote code execution as the web-server user. Entry names are also used unsafely, allowing directory traversal (../) to write files outside the intended extraction directory. 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 input validation and secure file handling within its automated update mechanism. The core of this flaw resides in the UpdateCE.php script, which is responsible for managing system updates by downloading archives from remote sources. In versions preceding 1.5, the implementation fails to enforce strict security controls during the extraction process. Specifically, when a ZIP archive is downloaded and processed, the application extracts its contents directly into the web root directory without performing any validation on file types or verifying safe extraction paths. This lack of sanitization allows an attacker who can influence the update source or trigger the processing of a maliciously crafted archive to achieve remote code execution with the privileges of the web server process.
From a technical perspective, this vulnerability stems from two primary deficiencies: insecure direct object references in file path handling and insufficient validation of extracted content types. The application blindly trusts the internal structure of the provided ZIP file. It does not filter out directory traversal sequences such as ../ within entry names. Consequently, an attacker can craft a malicious archive containing files with paths that escape the intended target directory. This capability allows for arbitrary file write operations outside the web root or into sensitive system directories if permissions allow. Furthermore, by including PHP scripts in the payload, these files are written directly to locations accessible via HTTP requests. Once placed on disk, an attacker can invoke these scripts through a browser request, executing arbitrary code within the context of the web server user account.
The operational impact of this vulnerability is severe, as it leads to full system compromise. Remote Code Execution (RCE) grants attackers complete control over the underlying operating system depending on the privileges assigned to the web service process. This can result in data exfiltration, defacement, installation of backdoors or ransomware, and lateral movement within the network infrastructure. The ability to write files outside the intended directory exacerbates this risk by potentially allowing modification of configuration files, inclusion of malicious scripts into existing legitimate pages via path traversal, or disruption of system services located outside the web root. This aligns with CWE-94 Improper Control of Generation of Code (Code Injection) and CWE-22 Path Traversal: '..' Sequences in File Names, highlighting the fundamental errors in input validation and file access control mechanisms employed by the software.
In terms of threat modeling, this vulnerability facilitates attacks consistent with MITRE ATT&CK techniques such as T1505.003 Server Software Component: Web Shell, where attackers deploy malicious scripts to maintain persistent access. Additionally, the use of directory traversal relates to T1083 File and Directory Discovery or more specifically the exploitation of file system permissions through path manipulation. The attack vector typically requires some form of user interaction or privilege escalation within the CMS itself, such as having administrative credentials that allow triggering updates from untrusted sources, although in certain configurations where automatic updates are enabled without proper source verification, this could potentially be exploited remotely with minimal initial access depending on network exposure and configuration settings.
Mitigation strategies focus primarily on upgrading to version 1.5 or later, which addresses these flaws by implementing robust validation for file types and enforcing strict path constraints during extraction processes. Organizations running older versions must immediately apply the patch provided in the updated release. In environments where immediate patching is not feasible due to operational constraints, temporary mitigations should include restricting outbound network access from the web server to prevent it from downloading unverified archives, disabling the automatic update functionality if possible, and ensuring that file upload permissions are tightly controlled. Additionally, implementing a Web Application Firewall with rules capable of detecting directory traversal patterns in URL parameters or POST data may provide an additional layer of defense against exploitation attempts while permanent remediation is underway. Regular security audits and adherence to secure coding standards such as OWASP guidelines for input validation and output encoding are essential to prevent similar vulnerabilities in future development cycles.