Severity: moderate

Prototype Pollution



Versions of hoek prior to 4.2.1 and 5.0.3 are vulnerable to prototype pollution.

The merge function, and the applyToDefaults and applyToDefaultsWithShallow functions which leverage merge behind the scenes, are vulnerable to a prototype pollution attack when provided an unvalidated payload created from a JSON string containing the __proto__ property.

This can be demonstrated like so:

var Hoek = require('hoek');
var malicious_payload = '{"__proto__":{"oops":"It works !"}}';
var a = {};
console.log("Before : " + a.oops);
Hoek.merge({}, JSON.parse(malicious_payload));
console.log("After : " + a.oops);

This type of attack can be used to overwrite existing properties causing a potential denial of service.


Update to version 4.2.1, 5.0.3 or later.

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Advisory timeline

  1. reported

    Initial report by HoLyVieR
    Apr 20th, 2018
  2. published

    Advisory published
    Feb 15th, 2018