Review reviewHigh

CVE-2026-5079

multer

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 mini...

CVSS: 7.5
EPSS: 0.28%
CISA KEV: Not listed
Published: 2026.06.15

PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV

Exploit probability0.28%

Technical severityCVSS 7.5

Vulnerability overview

Affected product and versions

Product: multer
Affected versions: 1.0.0, 3.0.0-alpha.1, >= 1.0.0 < 2.2.0, 3.0.0
Fixed versions: 2.2.0

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide

1
Identify
Confirm that multer and an affected version are present.
2
Prioritize
Combine exploitation signals with asset exposure and business criticality.
3
Remediate
Follow the vendor advisory or supported update path and preserve rollback options.
4
Verify
Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CWE: CWE-400