Webpack Dev Middleware is a crucial tool for developers using webpack, providing a seamless development experience by serving webpack assets directly from memory. Version 3.7.3 is a patch release building upon the stable 3.7.2, offering incremental improvements and bug fixes. A notable difference lies in the peer dependencies: version 3.7.2 declared support only for Webpack 4 ^4.0.0, while 3.7.3 expands compatibility to include Webpack 5 ^4.0.0 || ^5.0.0. This broadens the usability of the middleware for developers who have migrated or are planning to migrate to the latest major version of webpack.
The core functionality remains the same: it intercepts requests, compiles assets on demand, and serves them without writing to disk, resulting in faster iteration cycles during development. The underlying dependencies remain consistent between the two versions, ensuring a familiar environment for existing users. The release date jump from September 2019 (3.7.2) to December 2020 (3.7.3) suggests a period of rigorous testing and stabilization of features, culminating in a more robust version. While the unpacked size increased slightly from 40311 to 40623, this is likely due to the additional compatibility code and bug fixes, offering more value overall. Developers should upgrade to version 3.7.3 for the expanded Webpack 5 support, benefit from bug fixes, and maintain compatibility with emerging webpack ecosystems.
All the vulnerabilities related to the version 3.7.3 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.