CVE-2026-75327 in DocSys
Summary
by MITRE • 08/26/2026
In DocSys-master V2.02.85, the uploadMarkdownPic interface in src/com/DocSystem/controller/DocController.java has an arbitrary file upload vulnerability:
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 08/27/2026
The identified vulnerability resides within the DocSys-master application version 2.02.85, specifically affecting the uploadMarkdownPic endpoint implemented in the Java class src/com/DocSystem/controller/DocController.java. This component is designed to handle image uploads for markdown documents but fails to implement adequate validation mechanisms for file inputs. The core technical flaw is an arbitrary file upload vulnerability, which allows attackers to bypass intended restrictions and store malicious files on the server's filesystem or web directory without proper authorization checks or content verification.
From a technical perspective, this weakness typically stems from insufficient sanitization of user-supplied input regarding filename extensions, MIME types, or file contents. In many Java-based implementations using frameworks like Spring MVC or Struts, developers may rely solely on client-side validation or basic extension whitelists that can be easily circumvented by manipulating HTTP requests with tools such as Burp Suite or curl. An attacker could upload a script disguised as an image, for example, by appending malicious code to the file header or using double extensions like .jpg.jsp. If the server interprets these files based on their extension rather than their actual content structure, it may execute them when accessed via a web browser, leading to remote code execution.
The operational impact of this vulnerability is severe and multifaceted. Successful exploitation allows an unauthenticated attacker or any user with access to the upload interface to place arbitrary scripts onto the server. This can lead to full system compromise if the application runs under privileged accounts or lacks proper sandboxing. Attackers may deploy web shells, backdoors, or ransomware, effectively taking control of the underlying operating system and potentially pivoting to other systems within the network. Additionally, this vulnerability facilitates data exfiltration by allowing attackers to read sensitive files stored on the server if directory traversal is also possible due to poor path handling in the upload logic.
This flaw aligns with CWE-434, which describes an unrestricted upload of file with dangerous type, and CWE-20, indicating improper input validation where user-supplied data is not sufficiently verified before processing. In terms of offensive security frameworks, this vulnerability maps directly to MITRE ATT&CK technique T1505.003, known as Web Shell: Cloud Services or Server-Side Scripting, depending on the specific environment configuration. It represents a critical entry point for initial access and subsequent lateral movement within an enterprise network infrastructure.
Mitigation strategies must focus on implementing robust server-side validation controls. Developers should enforce strict whitelisting of allowed file extensions rather than relying on blacklists, which are prone to bypasses through encoding tricks or alternative valid extensions. It is crucial to validate the MIME type by inspecting the actual file signature magic bytes instead of trusting the Content-Type header sent by the client. Furthermore, uploaded files should be stored in a directory that does not have execute permissions and outside the web root if possible, ensuring they are served as static content rather than executable scripts. Renaming uploaded files to random identifiers can also prevent attackers from predicting file paths for subsequent exploitation attempts. Regular security audits and integration of static application security testing tools into the CI/CD pipeline will help detect such flaws early in the development lifecycle before deployment to production environments.