CVE-2026-87908: multiparty vulnerable to Denial of Service via unbounded part-header accumulation

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-09-11 · updated 2026-09-16
Weakness: CWE-400

Description

multiparty is a Node.js library for parsing multipart/form-data request bodies. In versions from 2.1.0 up to but not including 4.3.1, the parser does not bound the amount of memory used while accumulating the headers of a single multipart part. An unauthenticated attacker can send a single request whose part carries a very large volume of header bytes, forcing the parser to buffer all of them and exhausting the process memory, which crashes the server. This is a denial of service with no confidentiality or integrity impact. The issue is fixed in multiparty 4.3.1, which caps the size of the accumulated part headers. Users should upgrade to multiparty 4.3.1 or later.

Affected products

multiparty: from 2.1.0 before 4.3.1 — fixed in 4.3.1

How to fix

Upgrade to a fixed version: multiparty 4.3.1. Check the vendor advisory for mitigations.

References

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