{"uuid": "310fa769-b1a1-43fd-a81b-ef66c07e90c7", "vulnerability_lookup_origin": "1a89b78e-f703-45f3-bb86-59eb712668bd", "author": "9f56dd64-161d-43a6-b9c3-555944290a09", "vulnerability": "CVE-2026-61534", "type": "seen", "source": "https://gist.github.com/alon710/880dc77a6d2d63a35f137e7b084bf95b", "content": "# CVE-2026-61534: CVE-2026-61534: Prototype Pollution in confetti yayson JSON:API Deserialization Engine\n\n> **CVSS Score:** 9.1\n> **Published:** 2026-09-11\n> **Full Report:** https://cvereports.com/reports/CVE-2026-61534\n\n## Summary\nA critical prototype pollution vulnerability was discovered in the confetti yayson library prior to version 4.3.0. The library deserializes JSON:API structures into internal cache dictionaries mapped with standard JavaScript objects. An attacker can control the cache keys by supplying '__proto__' in properties like type or id, modifying the prototype of all JavaScript objects process-wide.\n\n## TL;DR\nUnauthenticated remote prototype pollution in confetti yayson allows process-wide logic corruption, Denial of Service, or Remote Code Execution via structured JSON:API documents.\n\n## Exploit Status: POC\n\n## Technical Details\n\n- **CWE ID**: CWE-1321\n- **Attack Vector**: Network (AV:N)\n- **CVSS Score**: 9.1 (Critical)\n- **Exploit Status**: Proof of Concept (PoC) Available\n- **CISA KEV Status**: Not Listed\n- **Impact**: Integrity and Availability (High)\n\n## Affected Systems\n\n- Applications running Node.js or browser environments deserializing JSON:API payloads with yayson versions <= 4.2.0\n- **yayson**: <= 4.2.0 (Fixed in: `4.3.0`)\n\n## Mitigation\n\n- Upgrade confetti yayson package to version 4.3.0 or higher.\n- Run Node.js process with --disable-proto=throw or --disable-proto=delete.\n- Sanitize incoming client payloads at the gateway or middleware layer to drop __proto__, constructor, and prototype keys.\n\n**Remediation Steps:**\n1. Identify all Node.js applications referencing yayson in package.json.\n2. Run npm install yayson@4.3.0 or yarn add yayson@4.3.0.\n3. Deploy perimeter validation rules to screen incoming application/vnd.api+json requests.\n4. Restart running application services with the V8 protection flag node --disable-proto=throw.\n\n## References\n\n- [Official GitHub Security Advisory](https://github.com/confetti/yayson/security/advisories/GHSA-325j-mg25-8q58)\n- [Fix Pull Request](https://github.com/confetti/yayson/pull/111)\n- [Fix Patch Commit](https://github.com/confetti/yayson/commit/e460162d5a3ebac86424bead7424957c36f8dff9)\n- [Release v4.3.0 Tag](https://github.com/confetti/yayson/releases/tag/v4.3.0)\n\n\n---\n*Generated by [CVEReports](https://cvereports.com/reports/CVE-2026-61534) - Automated Vulnerability Intelligence*", "creation_timestamp": "2026-09-14T16:32:16.944218Z"}