Webpack Dev Middleware experienced a notable update moving from version 3.1.3 to 3.2.0, offering developers some key improvements. A primary focus was on dependency updates, impacting the internal workings and potentially enhancing stability. The webpack-log dependency saw an upgrade from version 1.0.1 to 2.0.0, suggesting improvements or feature additions to the logging mechanisms which could aid debugging. The mime dependency was bumped from ^2.1.0 to ^2.3.1, potentially improving handling of various MIME types which helps with delivering different asset types correctly in the browser.
In the *devDependencies* section, key upgrades occurred. eslint jumped from version 4.0.0 to 5.4.0, suggesting enhanced code linting and style enforcement. A significant upgrade was for webpack itself, moving from version 4.2.0 to 4.17.1, this indicates bug fixes, performance improvements or new features within webpack that the middleware now utilizes and developers consuming it may benefit from this. supertest, employed for integration testing, updated from 3.0.0 to 3.1.0 possibly improving the testing strategies behind the updates of the software. Additionally, file-loader advanced from 1.1.10 to 2.0.0 suggesting improved capacity to handle file emitting for testing purposes. The addition of standard-version":"^4.4.0" shows the project adopted a standardized versioning and release process. These dependency updates reflect the ongoing effort to modernize and enhance the underlying development environment.
All the vulnerabilities related to the version 3.2.0 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.