CVE-2026-8161: multiparty vulnerable to Denial of Service via Prototype Pollution leading to Uncaught Exception

Published May 12, 2026
·
Updated

Impact

multiparty@4.2.3 and lower versions are vulnerable to denial of service via uncaught exception. By sending a multipart/form-data request with a field name that collides with an inherited Object.prototype property (e.g., proto, constructor, toString), the parser invokes .push() on the inherited prototype value rather than an array, throwing a TypeError that propagates as an uncaught exception and crashes the process. Any service accepting multipart uploads via multiparty is affected.

Patches

Users should upgrade to multiparty@4.3.0 or higher.

Workarounds

None.

Other sources

multiparty@4.2.3 and lower versions are vulnerable to denial of service via uncaught exception. By sending a multipart/form-data request with a field name that collides with an inherited Object.prototype property such as proto, constructor, or toString, the parser invokes .push() on the inherited prototype value rather than an array, throwing a TypeError that propagates as an uncaught exception and crashes the process. Impact: any service accepting multipart uploads via multiparty is affected. Workarounds: none. Upgrade to multiparty@4.3.0 or higher.

— MITRE

Affected Software

3 affected componentsFixes available
npm/multiparty<=4.2.3
pillarjs Multiparty Node.js<4.3.0
npm/multiparty<=4.2.3
4.3.0

Remediation

Recommended actions to resolve this vulnerability, in priority order.

  1. Upgrade

    Upgrade npm/multiparty to a version that resolves this vulnerability.

    Fixed in 4.3.0
  2. Upgrade

    Upgrade multiparty to a version that resolves this vulnerability.

    Fixed in 4.3.0

Event History

May 12, 2026
CVE Published
via MITRE·08:50 AM
Data Sourced
via MITRE·08:50 AM
DescriptionSeverityWeakness
Data Sourced
via NVD·10:16 AM
DescriptionSeverityWeaknessAffected Software
May 18, 2026
Advisory Published
via GitHub·05:35 PM
Data Sourced
via GitHub·05:35 PM
DescriptionSeverityWeaknessAffected Software
Oct 13, 58358
Event
via FIRST·05:55 PM
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Frequently Asked Questions

1

What is the severity of CVE-2026-8161?

CVE-2026-8161 has a medium severity rating due to its potential to cause Denial of Service.

2

How do I fix CVE-2026-8161?

To mitigate CVE-2026-8161, upgrade to multiparty version 4.2.4 or higher.

3

What versions of multiparty are affected by CVE-2026-8161?

Multiparty versions 4.2.3 and lower are affected by CVE-2026-8161.

4

What type of attack does CVE-2026-8161 facilitate?

CVE-2026-8161 facilitates a Denial of Service attack via Prototype Pollution.

5

Is CVE-2026-8161 related to specific data types?

Yes, CVE-2026-8161 affects multipart/form-data requests with colliding field names.

Company

Resources

Contact

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CVE-2026-8161 - multiparty vulnerable to Denial of Service via Prototype Pollution leading to Uncaught Exception - SecAlerts