GitHub Advisoryadvisory · npm
GHSA-535w-7cp7-47q4 multer vulnerable to Denial of Service via oversized array index in field names
HIGH
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
- https://github.com/expressjs/multer/security/advisories/GHSA-535w-7cp7-47q4 web
- https://nvd.nist.gov/vuln/detail/CVE-2026-82333 advisory
- https://github.com/expressjs/multer/pull/1438 web
- https://github.com/expressjs/multer/commit/73c1759fa93b87366bc6dbd7abe1b80ddff7d27c web
- https://cna.openjsf.org/security-advisories.html web
- https://github.com/expressjs/multer package
- https://github.com/expressjs/multer/releases/tag/v2.3.0 web