Low [CVE-2026-84368] @hapi/joi: joi: Prototype pollution via untrusted input in schema configuration

joi is a schema description language and data validator for JavaScript.

From 16.0.0 until 17.13.6 and 18.2.5, the @hapi/joi package through 17.1.1 and the successor joi package contain prototype pollution in lib/messages.js, where exports.compile() and exports.merge() reuse inherited objects for attacker-controlled language keys supplied through messages(), message(), prefs({ messages }), Joi.extend({ messages }), or rule({ message }).

A language key named __proto__ writes properties onto Object.prototype, and constructor writes to the Object function's static properties. A consuming application that gates on the presence of an inherited property can take the wrong branch for every inspected object.

The flaw is not reachable from data that joi validates and requires an application to feed untrusted input directly into schema-construction configuration. A flaw was found in joi.

This vulnerability, known as prototype pollution, allows an attacker to inject properties into core JavaScript objects by supplying untrusted input directly into schema-construction configuration. This can lead to a consuming application taking incorrect execution paths, potentially altering its behavior in unexpected ways.

Affected products named by the advisory: Gatekeeper 3; Migration Toolkit for Containers; Red Hat Build of Podman Desktop; Red Hat Data Grid 8; and 9 more.