{"uuid": "5de48a51-efa0-414f-8ac6-af8641f6702a", "vulnerability_lookup_origin": "1a89b78e-f703-45f3-bb86-59eb712668bd", "author": "9f56dd64-161d-43a6-b9c3-555944290a09", "vulnerability": "CVE-2026-5079", "type": "seen", "source": "https://gist.github.com/alon710/e8e930bfaf0a04644c5861c1af92ed10", "content": "# CVE-2026-5079: CVE-2026-5079: Denial of Service via Uncontrolled Resource Consumption in Multer Multipart Parser\n\n> **CVSS Score:** 7.5\n> **Published:** 2026-06-17\n> **Full Report:** https://cvereports.com/reports/CVE-2026-5079\n\n## Summary\nCVE-2026-5079 is a high-severity Denial of Service (DoS) vulnerability in the Node.js package 'multer'. The vulnerability resides in how its internal dependency, 'append-field', processes deeply nested bracket structures in multipart form field names. If an attacker submits a field name with an excessive number of nested brackets, the parsing process crashes the Node.js runtime environment or exhausts system resources, causing a complete denial of service.\n\n## TL;DR\nA Denial of Service vulnerability exists in the multer library when parsing deeply nested bracket notations in form field names, leading to application crash or CPU exhaustion.\n\n## Exploit Status: POC\n\n## Technical Details\n\n- **CWE ID**: CWE-400\n- **Attack Vector**: Network\n- **CVSS v3.1**: 7.5\n- **EPSS Score**: 0.00278\n- **Impact**: Denial of Service (DoS)\n- **Exploit Status**: poc\n- **KEV Status**: Not Listed\n\n## Affected Systems\n\n- Applications utilizing multer >= 1.0.0 and < 2.2.0 on Node.js runtimes\n- Applications utilizing multer 3.0.0-alpha.1 on Node.js runtimes\n- **multer**: >= 1.0.0 < 2.2.0 (Fixed in: `2.2.0`)\n- **multer**: == 3.0.0-alpha.1 (Fixed in: `3.0.0-alpha.2`)\n\n## Mitigation\n\n- Upgrade multer dependency to version 2.2.0 or 3.0.0-alpha.2.\n- Configure limits.fieldNestingDepth to a restrictive non-infinite value.\n- Implement Web Application Firewall (WAF) filtering to drop payloads with highly recurring bracket syntax.\n\n**Remediation Steps:**\n1. Run the command 'npm install multer@latest' or 'npm install multer@2.2.0' depending on major version requirements.\n2. Search the codebase for multer configuration initialization.\n3. Modify initialization structures to explicitly pass 'limits: { fieldNestingDepth: 3 }'.\n4. Deploy custom Express error-handling middleware to intercept LIMIT_FIELD_NESTING errors and return 400 Bad Request.\n\n## References\n\n- [GitHub Security Advisory GHSA-72gw-mp4g-v24j](https://github.com/expressjs/multer/security/advisories/GHSA-72gw-mp4g-v24j)\n- [NVD CVE-2026-5079 Details](https://nvd.nist.gov/vuln/detail/CVE-2026-5079)\n- [CVE Org Portal CVE-2026-5079](https://www.cve.org/CVERecord?id=CVE-2026-5079)\n- [OpenJS Foundation CNA Advisory Bulletin](https://cna.openjsf.org/security-advisories.html)\n- [Multer Source Code Repository](https://github.com/expressjs/multer)\n- [Multer 2.1.1 to 2.2.0 Compare Patch Diff](https://github.com/expressjs/multer/compare/v2.1.1...v2.2.0.diff)\n\n\n---\n*Generated by [CVEReports](https://cvereports.com/reports/CVE-2026-5079) - Automated Vulnerability Intelligence*", "creation_timestamp": "2026-06-17T19:41:25.000000Z"}