CVE-2026-57658 in TemplateSpare Plugin
Summary
by MITRE • 06/26/2026
Administrator Arbitrary File Upload in TemplateSpare <= 4.2.0 versions.
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Analysis
by VulDB Data Team • 06/26/2026
This vulnerability represents a critical security flaw in TemplateSpare versions up to 4.2.0 that allows administrators to upload arbitrary files to the server through a misconfigured file upload mechanism. The issue stems from insufficient input validation and access control measures within the template management system, creating an attack surface where authenticated administrative users can bypass normal file type restrictions and execute malicious code on the target system. The vulnerability falls under CWE-434 which specifically addresses insecure file upload functionality, where the application fails to properly validate or restrict file types during the upload process.
The technical implementation of this flaw occurs when administrators attempt to upload template files through the web interface without proper sanitization of file extensions or content verification. Attackers can exploit this by uploading malicious files such as php shell scripts, aspx web shells, or other executable payloads that will be processed by the web server. The vulnerability is particularly dangerous because it requires only administrative privileges, which are typically more powerful than regular user accounts and often have elevated system access rights. This allows attackers who have compromised administrator credentials to achieve remote code execution on the target server.
The operational impact of this vulnerability extends beyond simple code execution as it provides persistent access to compromised systems that can be maintained across reboots and system restarts. Once an attacker gains access through this vector, they can establish backdoors, exfiltrate sensitive data, escalate privileges further within the network, or use the compromised server as a launching point for lateral movement attacks. The presence of such vulnerabilities in content management systems like TemplateSpare directly aligns with ATT&CK technique T1059 which covers command and script interpreter execution, allowing attackers to execute arbitrary code on the target system.
Organizations should immediately implement multiple layers of defense including strict file type validation, mandatory content inspection of uploaded files, implementation of secure file upload mechanisms that store files outside of web root directories, and regular security audits of all administrative interfaces. The solution must include proper input sanitization, file extension whitelisting, and content-type checking to prevent malicious files from being accepted. Additionally, implementing network segmentation, monitoring for unusual file upload patterns, and regular patch management practices are essential defensive measures. Organizations should also consider implementing web application firewalls that can detect and block suspicious file upload activities, as well as establishing privileged access management controls that limit administrative access to only necessary personnel through multi-factor authentication and role-based access controls.
The vulnerability demonstrates how seemingly minor oversights in file handling can create major security risks in web applications. This flaw represents a typical example of insufficient validation in the application's security architecture, where proper access control mechanisms fail to validate file content against known malicious patterns. The attack surface is particularly dangerous because it leverages legitimate administrative functionality while bypassing normal security controls that would otherwise prevent code execution on the server. Regular penetration testing and security assessments should specifically target file upload mechanisms as they represent one of the most common attack vectors in web applications, with similar vulnerabilities found across numerous content management systems and enterprise applications.