CVE-2022-25848 - A Potential Path Traversal Vulnerability in Static-Dev-Server: Exploit Details, Code Snippets, and Mitigation Measures

In this long-read, we will discuss the recent vulnerability found in all versions of the static-dev-server package. This vulnerability, identified as CVE-2022-25848, involves the potential for a path traversal attack, which could allow malicious users to access sensitive information by means of manipulating file paths.

CVE-2022-25848 arises because paths are joined from the user to the root directory and the assets for the path accessed are relative to that of the root directory. In this post, we will dive into the code snippets, exploit details, and mitigation measures to help protect against this vulnerability. Additionally, we will provide links to original references for further investigation.

Original Reference

Code Snippet

The vulnerability exists in the way the static-dev-server handles file paths. When joining the user-supplied path to the root directory, it may lead to potential path traversal attacks. The following code snippet illustrates the problematic code:

const http = require('http');
const path = require('path');
const url = require('url');
const fs = require('fs');

const ROOT_DIR = path.join(__dirname, process.argv[2] || '');

http.createServer((req, res) => {
  const reqPath = url.parse(req.url).pathname;
  const filePath = path.join(ROOT_DIR, reqPath); // Problematic code - vulnerable to path traversal attacks

  // ...
}).listen(300);

Note that the filePath variable is created by joining the ROOT_DIR with the user-provided reqPath, creating an opportunity for a malicious user to exploit path traversal vulnerability.

Exploit Details

A potential attacker can exploit this vulnerability by crafting a URL containing particular characters such as .., which can traverse up directory levels. For example, an attacker could use the following URL:

http://localhost:300/../../../../etc/passwd

This URL would move up four directory levels from the root directory and access the /etc/passwd file, which could potentially contain sensitive system information. If successful, the attacker would gain unauthorized access to sensitive data on the server.

Mitigation Measures

To mitigate this vulnerability, it is essential to properly validate and sanitize the user-supplied paths before joining them with the root directory. One possible solution is to use the path.normalize() function in Node.js to remove any directory traversal sequences from the path. Additionally, the server should restrict access to system files and resources.

Here is an example of a code snippet demonstrating the mitigation measures mentioned above

const http = require('http');
const path = require('path');
const url = require('url');
const fs = require('fs');

const ROOT_DIR = path.join(__dirname, process.argv[2] || '');

http.createServer((req, res) => {
  const reqPath = url.parse(req.url).pathname;
  const safePath = path.normalize(reqPath); // Sanitize user-supplied path
  const filePath = path.join(ROOT_DIR, safePath);

  // ...
}).listen(300);

This updated code snippet, utilizing the path.normalize() function, would prevent a path traversal attack by normalizing the user-supplied path before combining it with the server's root directory.

In conclusion, CVE-2022-25848 is a concerning vulnerability found in all versions of the static-dev-server package. It is vital to understand and implement necessary mitigation measures to protect against potential path traversal attacks. By applying the secure coding practices mentioned in this post, developers can help reduce the risks associated with this vulnerability.

Timeline

Published on: 11/29/2022 17:15:00 UTC
Last modified on: 12/01/2022 20:56:00 UTC