CVE-2021-46036: Arbitrary File Upload Leading to RCE in MCMS

Background

MCMS (Mingsoft Content Management System) is a Maven package that provides content management functionality for web applications. It allows users to upload and manage various types of files. However, a vulnerability in the component /ms/file/uploadTemplate.do of MCMS v5.2.4 allows attackers to upload arbitrary files, leading to remote code execution (RCE) on the server.

Vulnerability Detail

The vulnerability arises due to insufficient validation of user-uploaded files. Attackers can exploit this by uploading malicious files with executable code, which can then be executed on the server. This can result in unauthorized access, data breaches, and potential compromise of the entire system. The vulnerability has a CVSS score of 9.8, indicating its critical severity.

Workaround

As a temporary workaround, administrators can disable the file upload functionality in MCMS or implement additional server-side validation to ensure that only safe file types are allowed. Here is an example of server-side validation code in Java:

// Check file extension
String fileName = uploadedFile.getOriginalFilename();
String fileExtension = fileName.substring(fileName.lastIndexOf('.') + 1);
if (!allowedExtensions.contains(fileExtension)) {
    throw new SecurityException("Invalid file type");
}

// Check file content
byte[] fileContent = uploadedFile.getBytes();
if (!isSafeFileContent(fileContent)) {
    throw new SecurityException("Unsafe file content");
}

Conclusion

The arbitrary file upload vulnerability in MCMS v5.2.4 can lead to remote code execution on the server. It is crucial to upgrade to a patched version of MCMS that includes proper file upload validation to mitigate this vulnerability. For further support and assistance in vulnerability remediation, please contact DevNack.com.

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