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.
Metrics
Affected Vendors & Products
References
History
Tue, 16 Jun 2026 17:00:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| First Time appeared |
Expressjs
Expressjs multer |
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| CPEs | cpe:2.3:a:expressjs:multer:*:*:*:*:*:node.js:*:* cpe:2.3:a:expressjs:multer:3.0.0:alpha1:*:*:*:node.js:*:* |
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| Vendors & Products |
Expressjs
Expressjs multer |
Mon, 15 Jun 2026 16:30:00 +0000
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|---|---|---|
| Metrics |
ssvc
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Mon, 15 Jun 2026 14:00:00 +0000
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| 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 |
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| Metrics |
cvssV3_1
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Status: PUBLISHED
Assigner: openjs
Published: 2026-06-15T13:56:45.520Z
Updated: 2026-06-15T16:00:43.955Z
Reserved: 2026-03-28T19:04:56.443Z
Link: CVE-2026-5079
Updated: 2026-06-15T16:00:37.960Z
Status : Analyzed
Published: 2026-06-15T14:16:37.293
Modified: 2026-06-16T16:49:34.057
Link: CVE-2026-5079
No data.
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