Webpack-dev-middleware is a crucial tool for developers using Webpack, acting as a bridge between Webpack's output and a web server during development. Comparing versions 3.5.0 and 3.4.0, several nuances emerge. The core functionalities, as reflected in the dependencies, remain consistent: employing mime for handling MIME types, memory-fs for in-memory file system operations, webpack-log for logging, and range-parser for handling HTTP range requests. This suggests that the fundamental capabilities of serving compiled assets remain stable.
The devDependencies also mirror each other, indicating a consistent testing and development environment. This includes tools like nyc for coverage, mocha for testing, sinon for spies and stubs, eslint for code linting, and standard-version for version management. The development workflow and quality assurance processes appear unchanged between versions. Crucially, both versions maintain the same peerDependencies, requiring webpack version 4.0.0 or higher. This signifies continued compatibility with Webpack's core functionalities. Analyzing the dist object, version 3.5.0 features a slightly larger unpacked size (33716 bytes) compared to 3.4.0 (32706 bytes). This increase, though small, hints at possible additions, bug fixes, or performance enhancements made in the newer version. Also the releaseDate confirm that version 3.5.0 is newer since it was released on 2019-01-04T18:07:44.617Z after the release of version 3.4.0 on 2018-09-24T18:39:04.197Z. Developers should migrate to the latest version to profit of the features and fixes.
All the vulnerabilities related to the version 3.5.0 of the package
Path traversal in webpack-dev-middleware
The webpack-dev-middleware middleware does not validate the supplied URL address sufficiently before returning the local file. It is possible to access any file on the developer's machine.
The middleware can either work with the physical filesystem when reading the files or it can use a virtualized in-memory memfs filesystem. If writeToDisk configuration option is set to true, the physical filesystem is used: https://github.com/webpack/webpack-dev-middleware/blob/7ed24e0b9f53ad1562343f9f517f0f0ad2a70377/src/utils/setupOutputFileSystem.js#L21
The getFilenameFromUrl method is used to parse URL and build the local file path. The public path prefix is stripped from the URL, and the unsecaped path suffix is appended to the outputPath: https://github.com/webpack/webpack-dev-middleware/blob/7ed24e0b9f53ad1562343f9f517f0f0ad2a70377/src/utils/getFilenameFromUrl.js#L82 As the URL is not unescaped and normalized automatically before calling the midlleware, it is possible to use %2e and %2f sequences to perform path traversal attack.
A blank project can be created containing the following configuration file webpack.config.js:
module.exports = { devServer: { devMiddleware: { writeToDisk: true } } };
When started, it is possible to access any local file, e.g. /etc/passwd:
$ curl localhost:8080/public/..%2f..%2f..%2f..%2f../etc/passwd
root:x:0:0:root:/root:/bin/bash
daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin
bin:x:2:2:bin:/bin:/usr/sbin/nologin
sys:x:3:3:sys:/dev:/usr/sbin/nologin
sync:x:4:65534:sync:/bin:/bin/sync
games:x:5:60:games:/usr/games:/usr/sbin/nologin
The developers using webpack-dev-server or webpack-dev-middleware are affected by the issue. When the project is started, an attacker might access any file on the developer's machine and exfiltrate the content (e.g. password, configuration files, private source code, ...).
If the development server is listening on a public IP address (or 0.0.0.0), an attacker on the local network can access the local files without any interaction from the victim (direct connection to the port).
If the server allows access from third-party domains (CORS, Allow-Access-Origin: * ), an attacker can send a malicious link to the victim. When visited, the client side script can connect to the local server and exfiltrate the local files.
The URL should be unescaped and normalized before any further processing.