CVE-2026-76800 in DeDeCMS
Summary
by MITRE • 08/20/2026
A flaw has been found in DeDeCMS 3. Affected by this vulnerability is an unknown functionality of the file /include/dialog/select_media_post.php. Executing a manipulation of the argument uploadfile can lead to unrestricted upload. The attack can be executed remotely. The exploit has been published and may be used.
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Analysis
by VulDB Data Team • 08/20/2026
The identified vulnerability in DeDeCMS version 3 represents a critical security flaw located within the file handling logic of /include/dialog/select_media_post.php. This component is responsible for processing media uploads, specifically managing files submitted through the uploadfile argument. The core technical deficiency lies in insufficient validation and sanitization mechanisms applied to user-supplied input before it is processed by the server-side script. Due to this lack of rigorous checks on file extensions, content types, or destination directories, an attacker can manipulate the uploadfile parameter to bypass intended restrictions. This failure allows for unrestricted file uploads, meaning that malicious actors are not limited to uploading benign media files but can instead inject executable scripts such as PHP shells into the web directory structure.
From a technical perspective, this vulnerability is classified under CWE-434, which describes an Unrestricted Upload of File with Dangerous Type. The absence of proper server-side validation enables the execution of arbitrary code on the target system once the uploaded file is accessed or executed by the web server. This flaw fundamentally undermines the integrity and confidentiality of the hosted application because it provides a direct pathway for remote code execution. Since DeDeCMS was widely used in various enterprise environments, particularly in China, this vulnerability poses a significant risk to organizations relying on this content management system for their public-facing websites or internal portals.
The operational impact of exploiting this flaw is severe and multifaceted. An attacker can execute the exploit remotely without requiring any form of authentication, which classifies it as an unauthenticated remote code execution vector according to MITRE ATT&CK techniques such as T1505.003 (Web Shell). Once a web shell is successfully uploaded and deployed, the attacker gains persistent access to the underlying operating system. This allows for comprehensive control over the server, including the ability to read sensitive data, modify website content, install additional malware, or use the compromised host as a pivot point for further network intrusions. The fact that public exploits are available significantly lowers the barrier to entry for attackers, increasing the likelihood of automated scanning and widespread compromise across vulnerable instances.
Mitigation strategies must focus on immediate remediation and defensive hardening. The primary recommendation is to apply any official patches or updates provided by DeDeCMS if they address this specific issue in version 3. If no patch is available, administrators should consider upgrading to a supported version of the CMS that implements robust file upload controls. In the interim, network-level defenses such as Web Application Firewalls can be configured to detect and block requests containing suspicious patterns associated with file uploads or web shell activity. Additionally, strict server configuration practices are essential, including disabling script execution in directories designated for uploaded files and ensuring that default administrative interfaces are not exposed to the public internet. Regular vulnerability assessments and penetration testing should also be conducted to identify similar weaknesses in other components of the application stack.