CVE-2022-29623: Connect-Multiparty RCE Vulnerability

CVE-2022-29623 Overview

CVE-2022-29623 is an arbitrary file upload vulnerability affecting the file upload module of Express Connect-Multiparty version 2.2.0. This vulnerability allows attackers to execute arbitrary code via a specially crafted PDF file. The connect-multiparty package is a popular Express.js middleware used for handling multipart form data, commonly employed for file uploads in Node.js web applications.

It is important to note that the vendor has not verified this vulnerability report, which may affect the availability of official patches or mitigations.

Critical Impact

Attackers can upload malicious files that bypass validation, potentially leading to arbitrary code execution on the server. This could result in full system compromise, data exfiltration, or use of the server for further attacks.

Affected Products

• connect-multiparty version 2.2.0
• Express.js applications using connect-multiparty for file uploads
• Node.js web applications with multipart form handling via connect-multiparty

Discovery Timeline

• 2022-05-16 - CVE-2022-29623 published to NVD
• 2025-05-20 - Last updated in NVD database

Technical Details for CVE-2022-29623

Vulnerability Analysis

This vulnerability falls under CWE-434 (Unrestricted Upload of File with Dangerous Type), which represents a critical class of file upload vulnerabilities. The flaw exists in the file upload handling mechanism of the connect-multiparty middleware, which fails to properly validate and restrict file types during the upload process.

When a web application accepts file uploads without adequate validation, attackers can submit files with malicious content. In this case, the vulnerability specifically involves crafted PDF files that can trigger code execution when processed by the server or when interacting with other components of the application stack.

The attack requires local access and user interaction, suggesting the exploitation chain may involve social engineering or physical access to the target system. Once exploited, the vulnerability can impact the confidentiality, integrity, and availability of the affected system.

Root Cause

The root cause of this vulnerability is inadequate file type validation in the connect-multiparty file upload module. The middleware fails to properly sanitize and validate uploaded file content, relying potentially on file extensions or MIME types which can be easily spoofed by attackers. This allows malicious files disguised as legitimate PDFs to be uploaded and processed by the server.

Attack Vector

The attack vector for CVE-2022-29623 requires local access to the target system with user interaction. An attacker would craft a malicious PDF file containing embedded code or exploit payloads. When this file is uploaded through an application using the vulnerable connect-multiparty middleware, the malicious content can be executed on the server.

The exploitation typically involves:

1. Crafting a PDF file with embedded malicious code or polyglot content
2. Uploading the file through a web form that uses connect-multiparty
3. The server processes or stores the file without proper validation
4. The malicious payload executes, potentially compromising the server

For technical details regarding this vulnerability, refer to the GitHub release notes for version 2.2.0 and the npm package information.

Detection Methods for CVE-2022-29623

Indicators of Compromise

• Unusual PDF files uploaded to the server with executable or script content embedded
• Server logs showing file upload requests with suspicious file names or abnormal file sizes
• Unexpected process spawning or network connections following file upload operations
• Presence of files with PDF extensions containing non-PDF headers or embedded scripts

Detection Strategies

• Implement file content inspection to detect polyglot files or embedded scripts in uploaded PDFs
• Monitor application logs for repeated file upload attempts or uploads of files with suspicious characteristics
• Deploy web application firewalls (WAF) with rules to inspect uploaded file content
• Use endpoint detection and response (EDR) solutions to monitor for post-exploitation activity following file uploads

Monitoring Recommendations

• Enable detailed logging for all file upload operations including file metadata and source IP
• Monitor server processes for unexpected child process creation or script execution
• Track file system changes in upload directories for suspicious file modifications
• Implement alerting for uploads containing executable content or known exploit signatures

How to Mitigate CVE-2022-29623

Immediate Actions Required

• Review all applications using connect-multiparty 2.2.0 and assess exposure to file upload attacks
• Implement strict file type validation on both client and server side, verifying file content not just extensions
• Consider replacing connect-multiparty with actively maintained alternatives such as multer or formidable
• Apply the principle of least privilege to file upload directories, ensuring uploaded files cannot be executed

Patch Information

As of the last NVD update on 2025-05-20, the vendor has not verified this vulnerability report. No official patch has been confirmed. Organizations should evaluate alternative file upload middleware solutions or implement additional security controls to mitigate the risk.

For the latest information, monitor the connect-multiparty npm package and the GitHub repository.

Workarounds

• Implement server-side file content validation that inspects the actual file contents, not just MIME types or extensions
• Use a separate, isolated environment for processing uploaded files before moving them to production storage
• Configure the web server to prevent execution of files in upload directories by removing execute permissions
• Apply strict Content-Security-Policy headers and disable any unnecessary file processing features

# Configuration example - Restrict file upload directory permissions
chmod 644 /path/to/upload/directory/*
chown www-data:www-data /path/to/upload/directory

# Disable script execution in upload directory (Apache example)
# Add to .htaccess in upload directory
# Options -ExecCGI
# AddHandler cgi-script .php .py .pl .sh

# Nginx configuration to prevent execution in uploads
# location /uploads {
#     location ~ \.(php|py|pl|sh|cgi)$ {
#         deny all;
#     }
# }