Prototype Pollution

Description

An application object, method or module can be overwritten with malicious logic due to the lack of validations and the nature of the JavaScript language.

Impact

• Overwrite or pollute the behavior of existing methods in the application.
• Lead to dangerous vulnerabilities suchs as XSS, SQLi, RCE, among others.

Recommendation

• Implement integrity validations on the vulnerable objects.
• Restrict and Discourage the use harmful properties such as proto in the system objects.

Threat

Authenticated attacker from the Internet.

Expected Remediation Time

⌚ minutes.

Score

Default score using CVSS 3.1. It may change depending on the context of the src.

Base

• Attack vector: N
• Attack complexity: H
• Privileges required: L
• User interaction: N
• Scope: U
• Confidentiality: N
• Integrity: L
• Availability: N

Temporal

• Exploit code madurity: P
• Remediation level: U
• Report confidence: R

Result

• Vector string: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N/E:P/RL:U/RC:R
• Score:
  • Base: 3.1
  • Temporal: 2.8
• Severity:
  • Base: Low
  • Temporal: Low

Compliant code

There are no harmful functionalities on vulnerable objects

function modifyPrototype(moduleName, deleteMethod, newMethod) {
  var newMod = new moduleName;

  //Add new method to the object, without altering the original
  newMod.${newMethod} = function() {
      //Add functionality to object
  };

  return newMod;
}

Non compliant code

There are functionalities that can be overwritten due to insecure coding practices

function modifyPrototype(moduleName, deleteMethod, newMethod) {
  // modifying the prototype of a module from within another function
  var newMod = require(moduleName);
  delete newMod[deleteMethod];
  newMod.${newMethod} = function() {
      // function body that modifies the original method
  };

  module.exports = newMod;
}

Requirements

• 173.Discard unsafe inputs

Fixes

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