CVE-2021-47819: ProjeQtOr File Upload RCE Vulnerability

CVE-2021-47819 Overview

CVE-2021-47819 is a critical file upload vulnerability affecting ProjeQtOr Project Management version 9.1.4. The application fails to properly validate uploaded files, allowing guest users to upload malicious PHP files with arbitrary code execution capabilities. Attackers can upload a PHP script through the profile attachment section and execute system commands by accessing the uploaded file with a specially crafted request parameter.

Critical Impact

Unauthenticated attackers can achieve remote code execution on vulnerable ProjeQtOr installations by exploiting the unrestricted file upload functionality, potentially leading to complete system compromise.

Affected Products

• ProjeQtOr Project Management 9.1.4

Discovery Timeline

• 2026-01-15 - CVE CVE-2021-47819 published to NVD
• 2026-01-16 - Last updated in NVD database

Technical Details for CVE-2021-47819

Vulnerability Analysis

This vulnerability falls under CWE-434 (Unrestricted Upload of File with Dangerous Type). The file upload functionality in ProjeQtOr Project Management 9.1.4 lacks proper validation of file types, extensions, and content. This allows attackers to bypass any client-side restrictions and upload PHP files that contain malicious code. The vulnerability is particularly severe because it can be exploited by guest users who do not require authentication, making it accessible to any remote attacker with network access to the application.

The attack is network-accessible with low complexity, requiring no user interaction or privileges. Upon successful exploitation, an attacker gains the ability to execute arbitrary system commands in the context of the web server process, which typically leads to complete compromise of the underlying server and potentially the broader network infrastructure.

Root Cause

The root cause of this vulnerability is insufficient server-side validation of uploaded files in the profile attachment functionality. The application fails to:

1. Properly validate file extensions against a whitelist of allowed types
2. Check the actual content/MIME type of uploaded files
3. Restrict the upload directory from executing server-side scripts
4. Implement proper access controls on the uploaded file storage location

This combination of missing security controls allows PHP files to be uploaded and subsequently executed by directly accessing them through the web server.

Attack Vector

The attack leverages the profile attachment upload feature accessible to guest users. An attacker crafts a malicious PHP file containing command execution code (such as a web shell) and uploads it through the vulnerable endpoint. Once the file is stored on the server, the attacker can access it directly via a web request, including a specially crafted parameter to trigger command execution.

The vulnerability is exploited over the network without requiring any authentication or user interaction. The attacker only needs to know the location where uploaded files are stored, which is typically predictable or discoverable through reconnaissance. For detailed exploitation information, refer to the Exploit-DB #49919 entry.

Detection Methods for CVE-2021-47819

Indicators of Compromise

• Unusual PHP files appearing in upload or attachment directories that were not created by legitimate application processes
• Web server logs showing direct access to uploaded files with suspicious parameters (e.g., cmd, exec, shell)
• Unexpected outbound network connections from the web server process
• Process spawning activity originating from the web server (PHP) process, such as cmd.exe, /bin/sh, or other system shells

Detection Strategies

• Monitor web server access logs for requests to upload directories containing PHP files or files with double extensions
• Implement file integrity monitoring on upload directories to detect unauthorized file creation
• Deploy web application firewalls (WAF) with rules to detect PHP file upload attempts and web shell signatures
• Analyze HTTP request payloads for PHP code patterns in multipart form data

Monitoring Recommendations

• Enable verbose logging for all file upload operations within ProjeQtOr
• Configure SIEM alerts for anomalous file creation events in web application directories
• Monitor system process trees for child processes spawned by web server workers
• Implement network traffic analysis to detect command-and-control communications originating from the server

How to Mitigate CVE-2021-47819

Immediate Actions Required

• Upgrade ProjeQtOr Project Management to the latest available version that addresses this vulnerability
• Restrict guest user access to file upload functionality until the patch is applied
• Implement server-side file type validation using a whitelist approach
• Configure the web server to deny execution of scripts in upload directories
• Review existing uploaded files for any malicious content

Patch Information

Organizations should upgrade to a patched version of ProjeQtOr Project Management. Consult the ProjeQtOr official website for the latest security updates and release notes. Given the critical nature of this vulnerability, immediate patching is strongly recommended.

Workarounds

• Disable guest user access or remove upload permissions for unauthenticated users until patching is complete
• Configure .htaccess or equivalent web server configuration to prevent PHP execution in upload directories
• Implement a reverse proxy or WAF rule to block requests containing PHP file extensions in upload form data
• Rename the upload directory and restrict direct URL access to uploaded files by serving them through a download script

# Apache configuration to prevent PHP execution in uploads directory
# Add to .htaccess in the uploads folder
<Directory "/path/to/projeqtor/uploads">
    php_admin_flag engine Off
    <FilesMatch "\.php$">
        Require all denied
    </FilesMatch>
</Directory>