hapijs Joi up to 17.13.7/18.2.8 Messages Messages Compilation __proto__ prototype pollution

Summaryinfo

A vulnerability was found in hapijs Joi up to 17.13.7/18.2.8. It has been declared as critical. Impacted is the function Messages Compilation of the component Messages. Executing a manipulation of the argument __proto__ can lead to prototype pollution. This vulnerability is handled as CVE-2026-90771. The attack can be executed remotely. There is not any exploit available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability has been found in hapijs Joi up to 17.13.7/18.2.8 and classified as critical. This vulnerability affects the function Messages Compilation of the component Messages. The manipulation of the argument __proto__ with an unknown input leads to a prototype pollution vulnerability. The CWE definition for the vulnerability is CWE-1321. The product receives input from an upstream component that specifies attributes that are to be initialized or updated in an object, but it does not properly control modifications of attributes of the object prototype. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

joi before versions 17.13.8 and 18.2.9 contains a prototype pollution vulnerability in the messages compilation function that accepts __proto__ as an error code. Attackers can supply __proto__ keys in custom messages to replace the returned object's prototype, breaking downstream code relying on Object.prototype methods.

The advisory is shared for download at github.com. This vulnerability was named CVE-2026-90771 since 09/13/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1059.

Upgrading to version 17.13.8 or 18.2.9 eliminates this vulnerability.

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Productinfo

Vendor

• hapijs

Name

• Joi

Version

• 17.13.0
• 17.13.1
• 17.13.2
• 17.13.3
• 17.13.4
• 17.13.5
• 17.13.6
• 17.13.7
• 18.2.0
• 18.2.1
• 18.2.2
• 18.2.3
• 18.2.4
• 18.2.5
• 18.2.6
• 18.2.7
• 18.2.8

Website

• Product: https://github.com/hapijs/joi/

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