Multiparty

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.

Published: 2026-09-11T06:37:51.216Z
Updated: 2026-09-11T15:54:32.991Z

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 Content-Disposition header whose filename* parameter contains a malformed percent-encoding, the parser invokes decodeURI on the value without try/catch. The resulting URIError 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.

Published: 2026-05-12T09:05:12.591Z
Updated: 2026-05-12T12:33:12.647Z

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.

Published: 2026-05-12T08:50:37.685Z
Updated: 2026-05-12T12:32:10.127Z

multiparty@4.2.3 and lower versions are vulnerable to denial of service via regular expression backtracking in the Content-Disposition filename parameter parser. A crafted multipart upload with a long header value can cause regex matching to take seconds, blocking the event loop. Impact: any service accepting multipart uploads via multiparty is affected. Workarounds: limiting upload sizes at the proxy or gateway layer reduces but does not eliminate the attack surface, since a small header of around 8 KB is sufficient to trigger the vulnerable backtracking. Upgrade to multiparty@4.3.0 or higher.

Published: 2026-05-12T08:35:39.564Z
Updated: 2026-05-12T12:33:59.418Z