Hey folks, today we'll dive deep into a recently discovered vulnerability - CVE-2022-37621 - which involves a prototype pollution vulnerability within the resolveShims function in resolve-shims.js of Thlorenz's Browserify-shim v3.8.15. We'll take a closer look at how this vulnerability affects the code, discuss potential exploits, and provide links to original references for you to explore further.

First, let's take a brief look at the main culprit, the resolveShims function in resolve-shims.js. Here is the code snippet:

function resolveShims (files, opts) {
  var packagePath = path.dirname(files)
  var packageOpts = extend(opts)
  var fullPath = path.join(packagePath, opts.package || '')
  var packageData = require(fullPath)
  var shim = packageData['browserify-shim']

  // ... Rest of the implementation
}

This function is responsible for resolving the shims (third-party modules) of a package using Browserify-shim. It takes files and opts as input parameters and requires the package.json file based on the fullPath. It also extracts the browserify-shim configuration from the packageData and processes the same.

Now, the vulnerability. The prototype pollution issue lies in how the fullPath variable is constructed and passed to the require function. An attacker can maliciously craft the value of opts.package to pollute the prototypes of the module or other objects it interacts with. This could lead to unintended behavior, crashes, or even security issues, such as denial-of-service (DoS) attacks or remote code execution (RCE).

For example, consider a package with malicious content in the opts.package

{
  "__proto__": {
    "malicious_prop": "The vulnerability just got exploited."
  }
}

This package, when processed by the resolveShims function, would pollute the prototypes of objects it interacts with, and every object derived from those prototypes would inherit the malicious_prop property. This could lead to unexpected behavior and potentially open the application to various security threats.

To mitigate this vulnerability, it is crucial to sanitize and validate any user-supplied data before using it to construct the fullPath. One possible solution is to use a safe file path normalization library that eliminates malicious characters and sequences from the input.

As this issue affects Thlorenz's Browserify-shim v3.8.15, developers using this version of the library should upgrade to a patched version or consider alternative libraries that do not present this risk.

For more information and references, you can check out these links:

1. CVE-2022-37621: NVD
2. Thlorenz/browserify-shim

In conclusion, always remember to treat user-supplied data with caution and make sure to validate and sanitize it before using or processing it in your applications. While vulnerabilities such as prototype pollution can cause unexpected behavior, by understanding and identifying the vulnerable code, as well as keeping our dependencies up to date, we can mitigate their impact and maintain the security of our applications.

Timeline

Published on: 10/28/2022 20:15:00 UTC
Last modified on: 11/03/2022 14:31:00 UTC