{"vulnerability": "CVE-2026-54639", "sightings": [{"uuid": "41c2ad9f-0f18-49f8-91e1-5a37382152ca", "vulnerability_lookup_origin": "1a89b78e-f703-45f3-bb86-59eb712668bd", "author": "9f56dd64-161d-43a6-b9c3-555944290a09", "vulnerability": "CVE-2026-54639", "type": "seen", "source": "https://gist.github.com/alon710/f56e7fea90184a0067b486a540ca3738", "content": "# CVE-2026-54639: CVE-2026-54639: Prototype Pollution and Patch Bypass in style-dictionary\n\n> **CVSS Score:** 8.8\n> **Published:** 2026-07-28\n> **Full Report:** https://cvereports.com/reports/CVE-2026-54639\n\n## Summary\nA critical prototype pollution vulnerability (CVE-2026-54639) exists in style-dictionary versions 4.3.0 through 5.4.3 due to unsafe object traversal in the convertTokenData utility. Although a patch was released in version 5.4.4 targeting '__proto__', a complete bypass is possible using 'constructor.prototype', leading to persistent global prototype pollution and potential remote code execution.\n\n## TL;DR\nstyle-dictionary is vulnerable to prototype pollution via convertTokenData. An incomplete patch in v5.4.4 can be bypassed using constructor.prototype, allowing global runtime pollution.\n\n## Exploit Status: POC\n\n## Technical Details\n\n- **CWE ID**: CWE-1321\n- **Vulnerability Class**: Prototype Pollution\n- **CVSS v3.1 Score**: 8.8 (High)\n- **Attack Vector**: Local (escalatible to Remote)\n- **EPSS Score**: 0.00132 (3.12 percentile)\n- **Patch Status**: Incomplete (v5.4.4 bypass identified)\n- **CISA KEV Status**: Not listed\n\n## Affected Systems\n\n- style-dictionary NPM package\n- **style-dictionary**: >= 4.3.0, <= 5.4.3 (Fixed in: `5.4.4 (Incomplete fix)`)\n\n## Mitigation\n\n- Validate and sanitize all design token input keys before passing to the conversion function.\n- Override convertToTokenObject behavior or use Object.create(null) for dynamic dictionary construction.\n- Upgrade to a secure patched version once a complete remediation block is deployed.\n\n**Remediation Steps:**\n1. Identify applications utilizing style-dictionary's convertTokenData utility dynamically with user-controlled input.\n2. Deploy a custom input sanitizer regex pattern to block keys containing '__proto__', 'constructor', or 'prototype'.\n3. Refactor code to construct design token maps using secure JSON Schema validation.\n\n## References\n\n- [GHSA-vj5c-m527-mpff](https://github.com/style-dictionary/style-dictionary/security/advisories/GHSA-vj5c-m527-mpff)\n- [NVD - CVE-2026-54639](https://nvd.nist.gov/vuln/detail/CVE-2026-54639)\n\n\n---\n*Generated by [CVEReports](https://cvereports.com/reports/CVE-2026-54639) - Automated Vulnerability Intelligence*", "creation_timestamp": "2026-07-29T02:31:53.724323Z"}]}