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Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')

CVE-2026-8161

High
7.5/10

Summary

multiparty versions through 4.2.3 are vulnerable to Denial-of-Service (DoS) 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.

  • LOW
  • NETWORK
  • NONE
  • UNCHANGED
  • NONE
  • NONE
  • NONE
  • HIGH

CWE-1321 - Prototype Pollution

Prototype pollution is one of the lesser-known vulnerabilities. It allows attackers to abuse the rules of JavaScript by injecting properties into the general object “Object” in JS. Modifying the prototype of “Object” affects the behavior of all objects in the entire app, potentially resulting in denial of service, arbitrary code execution, cross-site scripting, etc.

References

Advisory Timeline

  • Published