CVE-2026-5079
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.
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Affected packages
Versions sourced from the GitHub Security Advisory.
| Package | Affected versions | Patched versions |
|---|---|---|
multernpm | >= 1.0.0, < 2.2.0 | 2.2.0 |
multernpm | >= 3.0.0-alpha.1, < 3.0.0-alpha.2 | 3.0.0-alpha.2 |
Affected products
3Patches
Vulnerability mechanics
References
4- cna.openjsf.org/security-advisories.htmlnvdVendor AdvisoryWEB
- github.com/advisories/GHSA-72gw-mp4g-v24jghsaADVISORY
- github.com/expressjs/multer/security/advisories/GHSA-72gw-mp4g-v24jnvdMitigationVendor AdvisoryWEB
- nvd.nist.gov/vuln/detail/CVE-2026-5079ghsaADVISORY
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