CVE-2026-77078
multer vulnerable to Denial of Service via crafted multipart field names
HIGH 7.5EPSS 0.5%
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
- multer
- CVSS v3.1 CNA
- 7.5 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - EPSS
- 0.49% chance of exploitation in the next 30 days, 41st percentile
- Published
- 2026-08-28
- Updated
- 2026-08-31
Proof-of-concept exploits (1)
- wtfkimi/CVE-2026-770780★ · 2026-09-21
Security advisories
- https://cna.openjsf.org/security-advisories.html
- expressjs/multer/security/advisories/GHSA-wc9g-mqfw-jrwm
- advisories/GHSA-wc9g-mqfw-jrwm