Overview
Version 1.6.1 of the Flash Payments package graphql-upload-minimal is vulnerable to prototype pollution. This vulnerability, located in the processRequest() function, allows an attacker to inject special property names into the operations.variables object and pollute global object prototypes, ultimately impacting the entire Node.js process.
Description
graphql-upload-minimal is a lightweight Node.js middleware package that implements the GraphQL multipart request specification, enabling file uploads in GraphQL servers. It parses multipart/form-data requests and maps uploaded files into the GraphQL operations object, making them accessible to resolvers.
The vulnerability exists in the processRequest() function, which handles multipart file upload requests. It processes a user-supplied map parameter that determines where uploaded files should be placed within the GraphQL operations.variables object.
The issue occurs because user-supplied property paths are not validated before being resolved and written into the target object. Special JavaScript property names such as __proto__, __constructor__, and prototype are not restricted, allowing crafted paths to traverse the prototype chain and modify Object.prototype.
Because Object.prototype is the base prototype from which most JavaScript objects inherit, altering it results in global prototype pollution across the Node.js process. Once polluted, manipulated properties may be inherited by all subsequently created objects for the lifetime of the process.
Impact
Because Object.prototype is the foundational prototype for most JavaScript objects, modifying it can affect the behavior of all Node.js processes. Since the impact extends across the entire Node.js process and persists until the service is restarted, it can potentially result in logic corruption, denial of service, or unintended privilege escalation.
Solution
Users should upgrade to graphql-upload-minimal version 1.6.3 or later, which can be found at https://github.com/flash-oss/graphql-upload-minimal/tree/master . The patched release introduces safeguards to prevent unsafe prototype-chain property assignments during multipart file upload processing.
Acknowledgements
Thanks to Maor Caplan from Alma Security for reporting this vulnerability. This document was written by Michael Bragg.
Vendor Information
Other Information
| CVE IDs: | |
| Date Public: | 2026-03-12 |
| Date First Published: | 2026-03-12 |
| Date Last Updated: | 2026-03-12 18:47 UTC |
| Document Revision: | 1 |
