Webpack Dev Middleware offers a streamlined solution for serving webpack assets during development. Comparing versions 4.0.2 and 4.0.1, developers will find largely consistent dependency structures. Both versions rely on the same core dependencies: mem for memoization, memfs for in-memory file system operations, mime-types for MIME type detection, range-parser for HTTP range header parsing, and schema-utils for schema validation. The peer dependency remains webpack ^4.0.0 || ^5.0.0 in both versions, ensuring compatibility with webpack 4 and 5.
The primary differentiating factor lies in the dist section, which indicates that version 4.0.2 has a slightly larger unpacked size (44795 bytes) than version 4.0.1 (44269 bytes). This hints at internal changes or bug fixes that contributed to the size increment. The newer release date for version 4.0.2 (2020-11-10T12:19:25.243Z compared to 2020-11-09T20:16:25.694Z) also signals a more recent patch or update that developers might want to incorporate for stability or the latest feature improvements. While the dependency lists are identical, developers should upgrade to 4.0.2 to benefit from any potential bug fixes or performance enhancements included in the newer version. Both versions provide the same core functionalities to serve webpack assets.
All the vulnerabilities related to the version 4.0.2 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.