CVE-2026-82333: Expressjs Multer

High severity, CVSS 7.5. EPSS: 0.5% chance of exploitation in the next 30 days.

multer is a middleware for handling multipart/form-data in Node.js. A small multipart request with two specially crafted text field names can make multer's field parser synchronously iterate a maximum-length sparse array, blocking the event loop so the process cannot handle other requests. A large numeric array index in the first field allocates a maximum-length sparse array, and a second field with a non-numeric key then triggers a full-length iteration inside the append-field dependency. All versions before 2.3.0 are affected, and this is a remotely triggerable denial of service. multer 2.3.0 adds an opt-in fieldArrayIndexLimit option that rejects oversized array indexes. Upgrade to multer 2.3.0 and set limits.fieldArrayIndexLimit to the largest array index your application needs to remediate.

Affected products

• Expressjs Multer: before 2.3.0 (fixed in 2.3.0)

Published 2026-08-28. Last modified 2026-09-02.