Prototype Pollution in lodash vulnerable CVE-2020-8203

[imhunterand]

Describe the bugs: 🐛

lodash is a modern JavaScript utility library delivering modularity, performance, & extras.
Affected versions of this package are vulnerable to Prototype Pollution. The function zipObjectDeep can be tricked into adding or modifying properties of the Object prototype. These properties will be present on all objects.

Prototype Pollution is a vulnerability affecting JavaScript. Prototype Pollution refers to the ability to inject properties into existing JavaScript language construct prototypes, such as objects. JavaScript allows all Object attributes to be altered, including their magical attributes such as __proto__, constructor and prototype. An attacker manipulates these attributes to overwrite, or pollute, a JavaScript application object prototype of the base object by injecting other values. Properties on the Object.prototype are then inherited by all the JavaScript objects through the prototype chain. When that happens, this leads to either denial of service by triggering JavaScript exceptions, or it tampers with the application source code to force the code path that the attacker injects, thereby leading to remote code execution.

PoC

const _ = require('lodash'); _.zipObjectDeep(['__proto__.z'],[123]) console.log(z) // 123

There are two main ways in which the pollution of prototypes occurs:

• Unsafe Object recursive merge
• Property definition by path

Unsafe Object recursive merge
The logic of a vulnerable recursive merge function follows the following high-level model:

merge (target, source)
foreach property of source

if property exists and is an object on both the target and the source merge(target[property], source[property]) else target[property] = source[property]

When the source object contains a property named __proto__ defined with Object.defineProperty() , the condition that checks if the property exists and is an object on both the target and the source passes and the merge recurses with the target, being the prototype of Object and the source of Object as defined by the attacker. Properties are then copied on the Object prototype.

Clone operations are a special sub-class of unsafe recursive merges, which occur when a recursive merge is conducted on an empty object: merge({},source). lodash and Hoek are examples of libraries susceptible to recursive merge attacks.

Affected environments

• The following environments are susceptible to a Prototype Pollution attack:
• Application server
• Web server
• Web browser

CVE-2020-8203
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:H
GHSA-p6mc-m468-83gw

[imhunterand]

Hi! There has been 2 years ago, can you approved this pull-request as merged