CVE-2026-5079multer vulnerable to Denial of Service via deeply nested field names
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No exploitation reported and no EPSS estimate yet.
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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.
- CVSS
- 7.5 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Weakness (CWE)
- CWE-400
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- openjs
- NVD analysis
- Analyzed
- Record last updated
- Jun 15, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
multer multer multer:multer (from the name) | from 1.0.0 before 2.2.0; 2.2.0 not affected; from 3.0.0-alpha.1 before 3.0.0-alpha.2; 3.0.0-alpha.2 not affected | CNA record |
expressjs multer expressjs:multer | from 1.0.0 before 2.2.0; 3.0.0 | NVD |
References
- https://github.com/expressjs/multer/security/advisories/GHSA-72gw-mp4g-v24jmitigation, vendor-advisory
- https://cna.openjsf.org/security-advisories.htmlvendor-advisory
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.