CVE-2026-5079

multer vulnerable to Denial of Service via deeply nested field names

Published Jun 15, 2026 CVSS 3.1 · 7.5 High EPSS < 1% KEV · Not listed
Description
Impact: multer versions 1.0.0 through 2.1.1 and 3.0.0-alpha.1 are vulnerable to a Denial of Service via deeply nested field names in multipart form data. The append-field dependency parses bracket notation in field names with no limit on nesting depth, allowing an attacker to force allocation of deeply nested object structures that consume CPU and memory. A single HTTP request with a crafted multipart body is sufficient to exploit this.

Patches: Users should upgrade to multer 2.2.0 (2.x line) or 3.0.0-alpha.2 (3.x prerelease) and configure the new limits.fieldNestingDepth option to the minimum depth their application requires.

Workarounds: Set limits.fields to a reasonable value to reduce the number of fields an attacker can send per request. This does not fully mitigate the issue but limits the impact.

Remediation

No solution or workaround provided in the CVE record

Tracking

Sign in to view the affected projects.

Advisories

Source ID Title
Github GHSA Github GHSA GHSA-72gw-mp4g-v24j Multer vulnerable to Denial of Service via deeply nested field names
History
Type Values Removed Values Added
First Time appeared Multer
Multer multer
Vendors & Products Multer
Multer multer
Type Values Removed Values Added
First Time appeared Expressjs
Expressjs multer
CPEs cpe:2.3:a:expressjs:multer:*:*:*:*:*:node.js:*:*
cpe:2.3:a:expressjs:multer:3.0.0:alpha1:*:*:*:node.js:*:*
Vendors & Products Expressjs
Expressjs multer
Type Values Removed Values Added
Metrics ssvc

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

Type Values Removed Values Added
Description Impact: multer versions 1.0.0 through 2.1.1 and 3.0.0-alpha.1 are vulnerable to a Denial of Service via deeply nested field names in multipart form data. The append-field dependency parses bracket notation in field names with no limit on nesting depth, allowing an attacker to force allocation of deeply nested object structures that consume CPU and memory. A single HTTP request with a crafted multipart body is sufficient to exploit this. Patches: Users should upgrade to multer 2.2.0 (2.x line) or 3.0.0-alpha.2 (3.x prerelease) and configure the new limits.fieldNestingDepth option to the minimum depth their application requires. Workarounds: Set limits.fields to a reasonable value to reduce the number of fields an attacker can send per request. This does not fully mitigate the issue but limits the impact.
Title multer vulnerable to Denial of Service via deeply nested 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
Jun 15, 2026, 4:00 PM
Reserved
Mar 28, 2026, 7:04 PM
Status
Analyzed
Published
Jun 15, 2026, 2:16 PM
Modified
Jun 17, 2026, 10:58 AM