GitHub Advisoryadvisory · npm

GHSA-535w-7cp7-47q4 multer vulnerable to Denial of Service via oversized array index in field names

HIGH Published 2026-09-08 Modified 2026-09-08 Official page ↗
Aliases
CVE-2026-82333
Ecosystem
npm
Packages
multer
Severity
High
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weaknesses
CWE-400
Reviewed
2026-09-08

Affected packages

• npm multer: < 2.3.0 → fixed in 2.3.0

Description

Impact multer is vulnerable to a Denial of Service (DoS) via a crafted array index in multipart field names. The `append-field` dependency parses bracket notation in field names, and a large numeric index such as `items[4294967294]` forces allocation of a maximum-length sparse array. A following field with a non-numeric key on the same base then converts that array to an object by iterating its full length, which consumes CPU synchronously and leaves the process unable to handle other requests. A single HTTP request with a crafted multipart body is sufficient to exploit this, and it affects multer 1.x and 2.x. Patches Users should upgrade to `2.3.0` and configure `limits.fieldArrayIndexLimit` to the minimum array index their application requires. Workarounds None.

Related

Alias · CVE (1)

  • CVE-2026-82333 multer is a middleware for handling multipart/form-data in Node.js. vulnerability

Weakness · CWE (1)

  • CWE-400 Uncontrolled Resource Consumption weakness

References