Comprehensive Technical Analysis of EUVD-2026-5007 (CVE-2026-25141)

Orval TypeScript Client Generation – JSFuck-Based Code Injection Vulnerability

1. Vulnerability Assessment and Severity Evaluation

Vulnerability Overview

EUVD-2026-5007 (CVE-2026-25141) is a critical code injection vulnerability in Orval, a popular TypeScript client generator for OpenAPI/Swagger specifications. The flaw stems from an incomplete fix for CVE-2026-23947, where the jsStringEscape function fails to properly sanitize a subset of non-alphanumeric characters, enabling arbitrary JavaScript execution via JSFuck obfuscation.

CVSS v4.0 Severity Analysis

Metric	Value	Explanation
Base Score	9.3 (Critical)	High impact on confidentiality, integrity, and availability.
Attack Vector (AV)	Network (N)	Exploitable remotely without physical/logical access.
Attack Complexity (AC)	Low (L)	No specialized conditions required.
Attack Requirements (AT)	None (N)	No user interaction or prior access needed.
Privileges Required (PR)	None (N)	No authentication required.
User Interaction (UI)	None (N)	Exploitable without victim interaction.
Confidentiality (VC)	High (H)	Arbitrary code execution can lead to data exfiltration.
Integrity (VI)	High (H)	Malicious code can modify application behavior.
Availability (VA)	High (H)	Denial-of-service or resource exhaustion possible.
Scope (SC/SI/SA)	Unchanged (N)	Exploitation does not extend beyond the vulnerable component.

Key Takeaways:

• Critical severity due to remote code execution (RCE) potential in generated TypeScript clients.
• Low attack complexity makes it highly exploitable in automated attacks.
• No authentication or user interaction required, increasing risk in CI/CD pipelines and API-driven applications.

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2. Potential Attack Vectors and Exploitation Methods

Exploitation Mechanism

The vulnerability arises from insufficient escaping in jsStringEscape, which fails to neutralize JSFuck-compatible characters ([]()!+). Attackers can craft malicious OpenAPI/Swagger specifications that, when processed by Orval, generate TypeScript clients executing arbitrary JavaScript.

JSFuck Obfuscation Technique

JSFuck is an esoteric JavaScript encoding method that constructs valid JavaScript using only six characters: [, ], (, ), !, and +. Example:

(![]+[])[+[]] // Evaluates to "f" (false[0])

An attacker can chain these characters to form any JavaScript payload, bypassing traditional sanitization.

Exploitation Steps

1. Craft a Malicious OpenAPI/Swagger Spec
   • Inject JSFuck-encoded payloads into schema descriptions, example values, or default parameters.
   • Example:

     paths:
       /malicious:
         get:
           responses:
             200:
               description: "![+!+[]]+[+[]]"  # JSFuck for "10"
     

2. Generate a TypeScript Client with Orval
   • When Orval processes the spec, the jsStringEscape function fails to escape JSFuck characters, embedding them in the generated client.
3. Trigger Arbitrary Code Execution
   • The generated client, when used in a web application, executes the obfuscated payload (e.g., via eval(), Function(), or dynamic imports).

Real-World Attack Scenarios

• Supply Chain Attacks
  • Compromised OpenAPI specs in public registries (e.g., SwaggerHub) could lead to widespread RCE in downstream applications.
• CI/CD Pipeline Exploitation
  • Automated Orval builds in CI/CD (e.g., GitHub Actions, GitLab CI) could execute malicious payloads during client generation.
• API Abuse
  • Attackers could submit crafted OpenAPI specs to API gateways or developer portals, leading to RCE in internal systems.

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3. Affected Systems and Software Versions

Vulnerable Versions

Product	Affected Versions	Fixed Versions
Orval	7.19.0 ≤ x < 7.21.0	7.21.0
Orval	8.0.0 ≤ x < 8.2.0	8.2.0

Impacted Use Cases

• TypeScript API Clients generated from OpenAPI/Swagger specs.
• Frontend Applications using Orval-generated clients (e.g., React, Angular, Vue).
• Backend Services integrating Orval clients (e.g., Node.js, Deno).
• CI/CD Pipelines automating client generation.

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4. Recommended Mitigation Strategies

Immediate Actions

1. Upgrade Orval Immediately

   • For v7.x users: Upgrade to 7.21.0 or later.
   • For v8.x users: Upgrade to 8.2.0 or later.
   • Verify the fix by checking the jsStringEscape function in packages/core/src/utils/string.ts.

2. Temporary Workarounds (If Upgrade Not Possible)

   • Input Validation: Manually sanitize OpenAPI specs before processing with Orval.
   • Static Analysis: Use tools like Spectral or OpenAPI linting to detect JSFuck patterns.
   • Runtime Protections: Deploy Content Security Policy (CSP) with unsafe-eval restrictions.

3. Secure Development Practices

   • Avoid Dynamic Code Evaluation: Replace eval() or Function() calls in generated clients with safer alternatives (e.g., JSON.parse).
   • Code Signing: Digitally sign generated clients to detect tampering.
   • Dependency Scanning: Integrate Dependabot, Snyk, or Trivy to detect vulnerable Orval versions.

Long-Term Recommendations

• Adopt OpenAPI Security Best Practices
  • Use OpenAPI Security Schemes (OAuth2, API keys) to restrict spec modifications.
  • Enforce schema validation before client generation.
• Enhance CI/CD Security
  • Immutable Builds: Pin Orval versions in package.json/yarn.lock.
  • Sandboxed Execution: Run Orval in isolated environments (e.g., Docker containers).
• Monitor for Exploitation Attempts
  • Log OpenAPI Spec Changes: Audit modifications to API definitions.
  • Anomaly Detection: Use SIEM tools (e.g., Splunk, ELK) to detect JSFuck patterns in API traffic.

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5. Impact on the European Cybersecurity Landscape

Regulatory and Compliance Implications

• GDPR (General Data Protection Regulation)
  • Article 32 (Security of Processing): Organizations must implement appropriate technical measures to prevent RCE vulnerabilities.
  • Article 33 (Data Breach Notification): Exploitation leading to data exfiltration may trigger 72-hour breach reporting requirements.
• NIS2 Directive (Network and Information Security)
  • Critical Infrastructure Operators (e.g., energy, healthcare, finance) must patch high-severity vulnerabilities within strict timelines.
  • Digital Service Providers (e.g., cloud platforms) must ensure secure API client generation.
• EU Cyber Resilience Act (CRA)
  • Software Bill of Materials (SBOM) Requirements: Organizations must track Orval dependencies to comply with vulnerability disclosure obligations.

Threat Landscape Considerations

• Supply Chain Risks
  • Orval is widely used in European fintech, healthcare, and government APIs, making it a high-value target for APT groups.
• Automated Exploitation
  • Botnets and exploit kits could leverage this vulnerability for large-scale attacks on European digital services.
• Cross-Border Impact
  • A single compromised OpenAPI spec could propagate RCE across multiple EU member states, necessitating coordinated CERT-EU responses.

Recommended EU-Specific Actions

• ENISA Coordination
  • National CSIRTs (e.g., CERT-FR, BSI, NCSC-NL) should issue alerts to critical sectors.
• Threat Intelligence Sharing
  • ECCC (European Cybersecurity Competence Centre) should facilitate IOC (Indicators of Compromise) sharing for JSFuck-based attacks.
• Public-Private Collaboration
  • EU Cybersecurity Act encourages joint vulnerability disclosure between Orval maintainers and European organizations.

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6. Technical Details for Security Professionals

Root Cause Analysis

The vulnerability originates in the jsStringEscape function, which was partially patched for CVE-2026-23947 but missed JSFuck-compatible characters. The function escapes:

• Single quotes (')
• Double quotes (")
• Backslashes (\)
• Newlines (\n, \r)

However, it fails to escape:

• Square brackets ([, ])
• Parentheses ((, ))
• Exclamation marks (!)
• Plus signs (+)

Proof-of-Concept (PoC) Exploitation

1. Malicious OpenAPI Spec Example

   openapi: 3.0.0
   info:
     title: "Malicious API"
     version: "1.0.0"
   paths:
     /exploit:
       get:
         responses:
           200:
             description: "![+!+[]]+[+[]]"  # JSFuck for "10"
   

2. Generated TypeScript Client (Vulnerable)

   // Auto-generated by Orval (v7.20.0)
   export const getExploit = () => {
     return fetch('/exploit').then(res => res.json());
   };
   // The description field is unsafely embedded in documentation or error handling.
   

3. Exploitation via Dynamic Code Execution
   • If the generated client uses eval() or Function() (e.g., for dynamic imports), the JSFuck payload executes:

     (![]+[])[+[]] // "f"
     (+!+[])+[+[]] // "10"
     

Detection and Forensics

• Static Analysis Signatures
  • Regex for JSFuck Patterns:

    /(!|\[|\]|\(|\)|\+){5,}/
    

  • YARA Rule for Malicious OpenAPI Specs:

    rule Orval_JSFuck_Exploit {
      strings:
        $jsfuck = /(!|\[|\]|\(|\)|\+){5,}/
      condition:
        $jsfuck in (0..filesize)
    }
    

• Runtime Detection
  • Monitor for eval() or Function() calls in generated clients.
  • Log OpenAPI spec modifications to detect tampering.

Advanced Mitigation Techniques

• Custom Sanitization Hooks
  • Override jsStringEscape in Orval’s configuration:

    import { jsStringEscape } from 'orval/utils';
    
    const customEscape = (str: string) =>
      jsStringEscape(str).replace(/[\[\]()!+]/g, '\\$&');
    
    // Apply in Orval config
    

• Sandboxed Execution
  • Use Node.js VM module or Web Workers to isolate client generation.
• OpenAPI Schema Whitelisting
  • Restrict allowed characters in description, example, and default fields.

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Conclusion

EUVD-2026-5007 (CVE-2026-25141) represents a critical RCE risk in Orval’s TypeScript client generation, exploitable via JSFuck obfuscation. Given its CVSS 9.3 severity, low attack complexity, and broad impact on European digital infrastructure, organizations must:

1. Patch immediately to Orval 7.21.0/8.2.0.
2. Audit OpenAPI specs for malicious payloads.
3. Enhance CI/CD security to prevent supply chain attacks.
4. Monitor for exploitation attempts via static/dynamic analysis.

Failure to mitigate this vulnerability could lead to data breaches, regulatory penalties, and widespread compromise of EU-based applications. Proactive patching and secure coding practices are essential to defend against this and similar threats.