CVE-2026-77078
multer vulnerable to Denial of Service via crafted multipart field names
- Published
- Aug 28, 2026
- Updated
- Aug 31, 2026
- Assigning CNA
- openjs
- Evidence observed
- Sep 21, 2026
Primary CVSS
nvd · CVSS 3.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HLow · next 30 days
- Percentile
- 21.9%
- Model date
- Sep 20, 2026
EPSS is a statistical estimate, not a certainty or a measure of impact. Combine it with CVSS, KEV status, exposure and your environment.
Summary
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.
Sources
1Example repository demonstrating how to exploit CVE-2026-77078 in multer, with usage instructions in English and Russian.
Responsible use
Use vulnerability information only on systems you own or are authorized to test. Kitploit links to public research metadata and does not store exploit code or malicious payloads.