Invesalius3 Webapp Exposed to Remote Code Execution

Overview of the Invesalius3 Vulnerability

The Invesalius3 web application, a popular tool for medical imaging, is facing a critical security vulnerability. This flaw potentially allows for Remote Code Execution (RCE), posing significant risks to users and systems relying on this platform. This article delves into the specifics of the vulnerability, including its entry points, exploitation methods, and possible mitigations.

Description of the Vulnerability

The vulnerability arises from improper input validation in the file upload feature of the Invesalius3 web application. Attackers can exploit this flaw to upload malicious files, ultimately leading to the execution of arbitrary code on the server. The attack can be conducted using unauthenticated requests, which makes it particularly dangerous.

Entry Point and Attack Vectors

The main entry point for this vulnerability is the file upload functionality. The application fails to adequately check the type of files being uploaded, allowing for unauthorized file types to be facilitated. The attack typically follows this flow:

User interacts with Invesalius3
    |
    +-->(1) User uploads a malicious file
    |
    +-->(2) Application fails to validate file type
    |
    +-->(3) Malicious payload executes code on server

Technical Analysis of the Exploit

To exploit this vulnerability, an attacker may use various payloads tailored to execute on the server after a successful upload. Consider the following example payload:

Here, we illustrate a simple PHP web shell, which an attacker could try to upload:

• Payload Example:
  • <?php system($_GET['cmd']); ?>

This PHP code snippet, if uploaded successfully, allows an attacker to execute system commands by accessing the compromised file through a web request, like so:

http://targetdomain.com/uploads/malicious_file.php?cmd=whoami

When this URL is accessed, it runs the whoami command on the server, revealing the privileges under which the web server runs.

Parameters and HTTP Methods

The vulnerable file upload functionality typically utilizes the following parameters:

• Parameter: file – This parameter is used to upload files.
• Method: POST – The malicious file is sent via an HTTP POST request.

Since the vulnerability is detected in an unauthenticated context, it is especially concerning. Any malicious actor can carry out the exploit without needing to log in, significantly increasing the risk to users of the Invesalius3 platform.

Mitigating the Remote Code Execution Vulnerability

Mitigation of the RCE vulnerability involves a few critical steps:

• Input Validation: Implement strict validation of uploaded files based on type and content. Whitelisting file types that can be uploaded (e.g., image files only) is crucial.
• File Handling: Ensure that files are stored outside of the web root or that PHP execution is disabled in upload directories to prevent execution of uploaded files.
• Monitoring and Logging: Regular monitoring and logging of file upload activity can help to identify malicious attempts and enhance response capabilities.

These mitigation strategies should be part of a broader security framework that includes regular vulnerability assessments and updates of the web application.

Conclusion

In summary, the discovered RCE vulnerability within the Invesalius3 web application highlights the critical importance of secure file handling practices. Organizations using this software need to act swiftly to mitigate risks associated with the vulnerability.

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References: Exploit-DB, https://www.exploit-db.com/exploits/52076