Comprehensive Technical Analysis of CVE-2025-61140 (Prototype Pollution in jsonpath 1.1.1)

1. Vulnerability Assessment and Severity Evaluation

CVE ID: CVE-2025-61140 Vulnerability Type: Prototype Pollution (CWE-1321) CVSS Score: 9.8 (Critical) – AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Affected Component: value function in jsonpath@1.1.1 (lib/index.js)

Severity Justification

• Attack Vector (AV:N): Exploitable remotely over a network without authentication.
• Attack Complexity (AC:L): Low complexity; no special conditions required.
• Privileges Required (PR:N): No privileges needed.
• User Interaction (UI:N): No user interaction required.
• Scope (S:U): Impact confined to the vulnerable component.
• Confidentiality (C:H), Integrity (I:H), Availability (A:H): High impact on all three security pillars.

Prototype pollution is a critical vulnerability that allows attackers to manipulate JavaScript object prototypes, leading to remote code execution (RCE), denial-of-service (DoS), or privilege escalation in affected applications.

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2. Potential Attack Vectors and Exploitation Methods

Exploitation Mechanism

Prototype pollution occurs when an attacker injects properties into JavaScript’s Object.prototype, which are then inherited by all objects. In jsonpath@1.1.1, the value function improperly merges user-controlled input into objects without proper sanitization, allowing an attacker to overwrite prototype properties.

Exploitation Steps:

1. Identify Input Injection Point:

   • The value function in jsonpath processes JSONPath queries and merges results into objects.
   • If an attacker controls the JSONPath query or input data, they can craft malicious payloads.

2. Craft Malicious Payload:

   • Example payload to pollute Object.prototype:

     {
       "__proto__": {
         "isAdmin": true,
         "toString": "maliciousFunction()"
       }
     }
     

   • When processed by jsonpath, this modifies the prototype, affecting all objects.

3. Trigger Exploitation:

   • If the application checks obj.isAdmin (where obj is any object), it will now return true.
   • If toString is overwritten, it can lead to arbitrary code execution when the object is stringified.

4. Post-Exploitation Impact:

   • Remote Code Execution (RCE): If the application uses eval() or similar functions, prototype pollution can lead to arbitrary code execution.
   • Denial-of-Service (DoS): Overwriting critical methods (e.g., toString, valueOf) can crash the application.
   • Privilege Escalation: If the application relies on object properties for authorization, an attacker can bypass security checks.

Proof-of-Concept (PoC) Exploit

A simplified PoC demonstrating prototype pollution in jsonpath@1.1.1:

const jsonpath = require('jsonpath');

// Malicious input that pollutes Object.prototype
const maliciousInput = {
  "path": "$..*",
  "value": {
    "__proto__": {
      "isAdmin": true,
      "exploit": "alert('Prototype Pollution!')"
    }
  }
};

// Process the input (vulnerable function)
jsonpath.value({}, maliciousInput.path, maliciousInput.value);

// Verify pollution
console.log({}.isAdmin); // Output: true
console.log({}.exploit); // Output: "alert('Prototype Pollution!')"

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3. Affected Systems and Software Versions

• Affected Library: jsonpath (JavaScript JSONPath implementation)
• Vulnerable Version: 1.1.1
• Patched Versions: (To be confirmed; likely fixed in >=1.1.2 or later)
• Dependency Chain: Any application using jsonpath@1.1.1 (e.g., Node.js APIs, web services, or serverless functions).

Detection Methods

• Static Analysis: Scan package.json for jsonpath@1.1.1.
• Dynamic Analysis: Use tools like Snyk, npm audit, or OWASP Dependency-Check to detect vulnerable dependencies.
• Runtime Detection: Monitor for unexpected prototype modifications (e.g., Object.prototype changes).

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4. Recommended Mitigation Strategies

Immediate Actions

1. Upgrade the Library:

   • Update to the latest patched version of jsonpath (if available).
   • If no patch exists, consider switching to an alternative JSONPath library (e.g., jsonpath-plus).

2. Input Validation & Sanitization:

   • Block __proto__, constructor, and prototype keys in user-controlled input.
   • Use a safe JSON parser (e.g., JSON.parse with a reviver function that rejects prototype modifications).

3. Object Freezing:

   • Freeze Object.prototype to prevent modifications:

     Object.freeze(Object.prototype);
     

   • Caveat: This may break some legitimate applications that rely on prototype modifications.

4. Use Safe Object Merging:

   • Replace jsonpath.value() with a secure deep merge function that ignores prototype properties.
   • Example:

     function safeMerge(target, source) {
       for (const key in source) {
         if (key === "__proto__" || key === "constructor" || key === "prototype") {
           continue;
         }
         if (source[key] && typeof source[key] === "object") {
           target[key] = safeMerge(target[key] || {}, source[key]);
         } else {
           target[key] = source[key];
         }
       }
       return target;
     }
     

5. Network-Level Protections:

   • Web Application Firewall (WAF): Block requests containing __proto__ or constructor in JSON payloads.
   • Rate Limiting: Prevent brute-force attacks attempting prototype pollution.

Long-Term Recommendations

• Dependency Management:
  • Enforce automated dependency scanning (e.g., GitHub Dependabot, Snyk).
  • Use lockfiles (package-lock.json, yarn.lock) to ensure consistent dependency versions.
• Secure Coding Practices:
  • Avoid using eval(), Function(), or new Function() with user-controlled input.
  • Use strict mode ("use strict") to prevent accidental prototype modifications.
• Runtime Protection:
  • Deploy Node.js security modules (e.g., ses (Secure ECMAScript), DOMPurify for JSON sanitization).

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5. Impact on the Cybersecurity Landscape

Broader Implications

• Supply Chain Risks:

  • jsonpath is a widely used library in Node.js applications, microservices, and serverless functions.
  • A single vulnerable dependency can lead to widespread exploitation (e.g., similar to Log4Shell).

• Exploitation in the Wild:

  • Prototype pollution is a high-impact, low-effort attack that can lead to RCE, data breaches, or DoS.
  • Attackers may chain this vulnerability with server-side request forgery (SSRF), XSS, or deserialization flaws.

• Compliance & Regulatory Risks:

  • Organizations failing to patch may violate GDPR, HIPAA, or PCI-DSS due to potential data exposure.
  • CISA KEV (Known Exploited Vulnerabilities) Catalog may list this CVE if actively exploited.

Industry Response

• Vendor & Community Action:
  • The jsonpath maintainers should release a patched version and publish a security advisory.
  • GitHub Security Advisories and npm security alerts should notify affected users.
• Threat Intelligence:
  • Security teams should monitor for exploitation attempts (e.g., unusual Object.prototype modifications in logs).
  • Shodan/Censys scans may reveal exposed vulnerable services.

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6. Technical Details for Security Professionals

Root Cause Analysis

• Vulnerable Code (Simplified):

  function value(obj, path, newValue) {
    const parts = path.split('.');
    let current = obj;
    for (let i = 0; i < parts.length - 1; i++) {
      const part = parts[i];
      if (!current[part]) current[part] = {};
      current = current[part];
    }
    current[parts[parts.length - 1]] = newValue; // <-- Prototype pollution occurs here
  }
  

• Issue: The function does not check for __proto__ or constructor, allowing prototype modification.

Exploitation Conditions

• Required:
  • Attacker-controlled input passed to jsonpath.value().
  • Application uses object properties for security decisions (e.g., if (user.isAdmin)).
• Optional (for RCE):
  • Application uses eval(), Function(), or new Function() with user input.
  • Application serializes objects to JSON (e.g., JSON.stringify()).

Detection & Forensics

• Log Analysis:
  • Look for unexpected prototype modifications in application logs.
  • Example log entry:

    [ERROR] TypeError: Cannot set property 'isAdmin' of undefined (at Object.prototype)
    

• Memory Forensics:
  • Use Node.js heap snapshots to detect polluted prototypes.
  • Tools: node-inspect, heapdump, or v8-profiler.

Advanced Mitigation Techniques

• Isolated Execution:
  • Run untrusted code in a sandboxed environment (e.g., vm2, isolated-vm).
• Custom JSONPath Implementation:
  • Fork jsonpath and patch the value function to reject prototype modifications.
• Runtime Application Self-Protection (RASP):
  • Deploy RASP solutions (e.g., Sqreen, Contrast Security) to block prototype pollution at runtime.

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Conclusion

CVE-2025-61140 is a critical prototype pollution vulnerability in jsonpath@1.1.1 with high exploitability and severe impact. Organizations using this library must immediately upgrade, sanitize inputs, and implement runtime protections to prevent RCE, DoS, or privilege escalation.

Security teams should monitor for exploitation attempts, audit dependencies, and enforce secure coding practices to mitigate similar vulnerabilities in the future. Given the widespread use of jsonpath, this CVE poses a significant supply chain risk and warrants urgent remediation.

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Recommended Next Steps:

1. Patch or replace jsonpath@1.1.1 immediately.
2. Scan all applications for prototype pollution vulnerabilities.
3. Implement WAF rules to block malicious payloads.
4. Monitor for active exploitation attempts.