Vulnerability · Published May 12, 2026 · Assigned by openjs
CVE-2026-8161multiparty vulnerable to Denial of Service via Prototype Pollution leading to Uncaught Exception
High 7.5
In plain English
A high-severity prototype pollution in multiparty from multiparty. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 41% of all known vulnerabilities). Ready-made attack tooling exists: public proof-of-concept code. Fixed versions are available - upgrade the affected package.
Official description
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | node-multiparty | no fix listed | DEBIAN-CVE-2026-8161 |
| Debian:13 | node-multiparty | no fix listed | DEBIAN-CVE-2026-8161 |
| Debian:14 | node-multiparty | 4.3.0-1 | DEBIAN-CVE-2026-8161 |
| Ubuntu:22.04:LTS | node-multiparty | no fix listed | UBUNTU-CVE-2026-8161 |
| Ubuntu:24.04:LTS | node-multiparty | no fix listed | UBUNTU-CVE-2026-8161 |
| Ubuntu:25.10 | node-multiparty | no fix listed | UBUNTU-CVE-2026-8161 |
| Ubuntu:26.04:LTS | node-multiparty | no fix listed | UBUNTU-CVE-2026-8161 |
| Ubuntu:26.10 | node-multiparty | no fix listed | UBUNTU-CVE-2026-8161 |
| npm | multiparty | 4.3.0 | GHSA-qxch-whhj-8956 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| multiparty | multiparty | 0 – through 4.2.3 |
Weakness: CWE-248, CWE-1321 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H