CVE-2026-82333: expressjs multer Uncontrolled Resource Consumption

Vulnerability summary

CVE-2026-82333 is a high (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in expressjs multer. EPSS estimates a 0.49% chance of exploitation in the next 30 days, higher than 40.6% of scored vulnerabilities.

Timeline

1. 28-08-2026
   PublishedVulnerability first disclosed.
2. 31-08-2026
   Last modifiedVulnerability information updated.

Description

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.

• CWE-400Uncontrolled Resource ConsumptionThe product does not properly control the allocation and maintenance of a limited resource.