Vulnerability Description
Impact: multer versions 1.0.0 through 2.1.1 and 3.0.0-alpha.1 are vulnerable to a Denial of Service via deeply nested field names in multipart form data. The append-field dependency parses bracket notation in field names with no limit on nesting depth, allowing an attacker to force allocation of deeply nested object structures that consume CPU and memory. A single HTTP request with a crafted multipart body is sufficient to exploit this. Patches: Users should upgrade to multer 2.2.0 (2.x line) or 3.0.0-alpha.2 (3.x prerelease) and configure the new limits.fieldNestingDepth option to the minimum depth their application requires. Workarounds: Set limits.fields to a reasonable value to reduce the number of fields an attacker can send per request. This does not fully mitigate the issue but limits the impact.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Expressjs | Multer | >= 1.0.0, < 2.2.0 |
Related Weaknesses (CWE)
References
- https://cna.openjsf.org/security-advisories.htmlVendor Advisory
- https://github.com/expressjs/multer/security/advisories/GHSA-72gw-mp4g-v24jMitigationVendor Advisory
FAQ
What is CVE-2026-5079?
CVE-2026-5079 is a vulnerability with a CVSS score of 7.5 (HIGH). Impact: multer versions 1.0.0 through 2.1.1 and 3.0.0-alpha.1 are vulnerable to a Denial of Service via deeply nested field names in multipart form data. The append-field dependency parses bracket not...
How severe is CVE-2026-5079?
CVE-2026-5079 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-5079?
Check the references section above for vendor advisories and patch information. Affected products include: Expressjs Multer.