CVE-2026-84367
LowCVSS 3.7Summary
In the joi library, there is a vulnerability in the internals.rename() implementation used by object().rename(). It allows creating a schema that, using a regular expression and a Joi.expression() or Joi.x() target with match data interpolation, can set the prototype of the object returned by validate() to __proto__ instead of creating an own key.
Risk Assessment
An attacker can influence the prototype of the object returned by validation, potentially leading to unexpected application behavior, but the global Object.prototype is not modified.
Recommendation
Update the joi library to version 17.13.5 or 18.2.4, which contain the fix.
Other vulnerabilities in joi
See all- CVE-2026-84368Low
The joi library (and @hapi/joi) has a prototype pollution vulnerability in lib/messages.js. The exports.compile() and exports.merge() functions reuse inherited objects for attacker-controlled language keys, allowing properties to be written to Object.prototype.
- CVE-2026-48038Medium
A vulnerability in the joi library (versions before 17.13.4 and 18.2.1) allows a DoS attack by sending deeply nested JSON or objects with recursive link() schemas. Calling validate() without try/catch in a request handler can cause an unhandled RangeError and potentially crash the process.
Original NVD description (English source)
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.