Threat Intelligence Database

stream-json is a micro-library of stream components for processing JSON and JSONC with a minimal memory footprint. Prior to 3.6.0, Assembler materializes object properties with plain assignment, so an input key named __proto__ invokes the inherited setter and causes parsed object prototype replacement instead of creating an own data property. Applications that make authorization or feature decisions from inherited values can therefore consume attacker-controlled properties, and a null prototype can disrupt code that expects Object.prototype methods. The researcher treats parsing untrusted JSON as part of the project contract, while the maintainer states that documented inputs are locally owned dumps, exports, or logs and characterizes the attack vector as local. The global Object.prototype is not polluted. This issue is fixed in version 3.6.0.

CVE-2026-104182 is an inefficient algorithmic complexity vulnerability in the JSONC parser and verifier components of the stream-json library prior to version 3.6.0. The issue occurs because the parser restarts scanning for comment terminators from the opening slash whenever a block or line comment spans multiple input chunks, causing quadratic CPU usage and potentially stalling the Node.js event loop. This vulnerability affects only JSONC parsing, not plain JSON parsing. The vulnerability is considered local because the JSONC input is typically user-controlled or locally owned configuration data. The issue is fixed in version 3.6.0.