CVE-2026-5079
highpriority · track · 0EPSS 0.003 · 20 %ileDEEUUSEPSS · scored 2026-10-27
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
Technical severity, 0–10. One row per scoring source.
base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · medium–high · 6.9–7.5
ssvc
A stakeholder decision — act, attend, or track — from exploitation and impact.
weaknesses
The CWE weakness classes this flaw belongs to.
affected products (11)
Products and version ranges known to be affected.
advisories (2)
Vendor and ecosystem advisories describing this.
- WID-SEC-W-2026-2488IBM App Connect Enterprise: Mehrere SchwachstellenDeutsch2026-07-22csaf · cert_bundDE
Ein Angreifer kann mehrere Schwachstellen in IBM App Connect Enterprise ausnutzen, um einen Denial of Service Angriff durchzuführen, um Informationen offenzulegen, um Dateien zu manipulieren, um einen Cross-Site Scripting Angriff durchzuführen, und um Sicherheitsvorkehrungen zu umgehen.
- GHSA-72gw-mp4g-v24jMulter vulnerable to Denial of Service via deeply nested field names2026-06-17ghsa · osvUS
### Impact Multer is vulnerable to a Denial of Service (DoS) via deeply nested field names in multipart form data. The `append-field` dependency parses bracket notation in field names (e.g., `a[b][c]`) 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 `2.2.0` and configure `limits.fieldNestingDepth` 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.
also known as (3)
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sources
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references (6)
External citations — patches, advisories, analysis.
- https://cna.openjsf.org/security-advisories.htmlcnnvd
- https://github.com/expressjs/multer/security/advisories/GHSA-72gw-mp4g-v24jcnnvd
- https://cna.openjsf.org/security-advisories.htmlenisa_euvd
- https://github.com/expressjs/multer/security/advisories/GHSA-72gw-mp4g-v24jenisa_euvd
- https://cna.openjsf.org/security-advisories.htmlVendor Advisorynvd
- https://github.com/expressjs/multer/security/advisories/GHSA-72gw-mp4g-v24jMitigationVendor Advisorynvd
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