CVE-2026-82333

multer vulnerable to Denial of Service via oversized array index in field names

Published Aug 28, 2026 CVSS 3.1 · 7.5 High EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-535w-7cp7-47q4 multer vulnerable to Denial of Service via oversized array index in field names
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Expressjs
Expressjs multer
CPEs cpe:2.3:a:expressjs:multer:*:*:*:*:*:node.js:*:*
Vendors & Products Expressjs
Expressjs multer
Type Values Removed Values Added
First Time appeared Multer
Multer multer
Vendors & Products Multer
Multer multer
Type Values Removed Values Added
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.
Title multer vulnerable to Denial of Service via oversized array index in field names
Weaknesses CWE-400
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
openjs
Published
Updated
Aug 31, 2026, 6:39 PM
Reserved
Aug 28, 2026, 3:22 PM
Status
Analyzed
Published
Aug 28, 2026, 10:16 PM
Modified
Sep 2, 2026, 2:45 PM