high7.5
CVE-2026-77078
multer vulnerable to Denial of Service via crafted multipart field names
Impact
multer is a middleware for handling multipart/form-data in Node.js. A small multipart request containing two specially crafted text field names can cause an uncaught RangeError (Invalid array length) that terminates the Node.js process. The first field uses a very large numeric array index to allocate a maximum-length sparse array, and a second field then pushes past that length, which throws inside the append-field dependency and is not caught by multer. All versions before 2.3.0 are affected, and the issue is a remotely triggerable denial of service. The issue is fixed in multer 2.3.0. Upgrade to multer 2.3.0 to remediate.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| npm | multer | < 2.3.0 | 2.3.0 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Expressjs | Multer | before 2.3.0 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/advisories/GHSA-wc9g-mqfw-jrwm
- https://github.com/expressjs/multer/security/advisories/GHSA-wc9g-mqfw-jrwm
- https://nvd.nist.gov/vuln/detail/CVE-2026-77078
- https://github.com/expressjs/multer/commit/87a584e8c8d4da873292635fa1d8c4d78d985b76
- https://cna.openjsf.org/security-advisories.html
- https://github.com/expressjs/multer/releases/tag/v2.3.0