CVE-2026-84367: Hapijs Joi

Low severity, CVSS 3.7. EPSS: 0.4% chance of exploitation in the next 30 days.

joi is a schema description language and data validator for JavaScript. From 16.0.0 until 17.13.5 and 18.2.4, joi's lib/types/keys.js internals.rename() implementation used by object().rename() permits a schema that renames keys with a regular-expression source and a Joi.expression() or Joi.x() target that interpolates the pattern's own match data, combined with { multiple: true }, to derive a target from an attacker-controlled input key. An attacker can send x-__proto__ with an object value, causing the target to render as __proto__ and set the prototype of the object returned by validate() instead of creating an own key. The global Object.prototype is not modified, so the effect is confined to the object returned by that validation call. Static-string targets and schemas using the default { multiple: false } are not affected. This issue is fixed in versions 17.13.5 and 18.2.4.

Affected products

• Hapijs Joi: from 16.0.0, before 17.13.5 (fixed in 17.13.5); from 18.0.0, before 18.2.4 (fixed in 18.2.4)

Published 2026-09-01. Last modified 2026-09-09.