Esno is a lightweight and efficient tool designed for running TypeScript and JavaScript Node.js applications, leveraging the speed of esbuild for blazing-fast transpilation. Version 0.6.0 introduces notable improvements and additions compared to the previous stable version, 0.5.0. A key change is the update to esbuild, moving from version ^0.9.2 to ^0.12.5, providing developers with access to the latest optimizations, bug fixes, and features available in esbuild. This upgrade directly impacts performance and compatibility with newer language features. Another significant addition in version 0.6.0 is the inclusion of the "cross-spawn" dependency at version ^7.0.3. This dependency likely enhances cross-platform compatibility, ensuring esno functions reliably across different operating systems. The use of cross-spawn suggests improved handling of child processes, which is a crucial aspect when running Node.js applications in various environments. Furthermore, esbuild-register is updated from version ^2.2.0 to ^2.5.0, potentially addressing improvements and bug fixes related to the on-the-fly transpilation process. The updated dependencies, coupled with the increase in unpacked size from 2416 to 2465 bytes, indicate that version 0.6.0 brings tangible enhancements over its predecessor, offering a smoother and more robust development experience. The release date of version 0.6.0 is May 28, 2021, while the previous version was released on March 15, 2021.
All the vulnerabilities related to the version 0.6.0 of the package
esbuild enables any website to send any requests to the development server and read the response
esbuild allows any websites to send any request to the development server and read the response due to default CORS settings.
esbuild sets Access-Control-Allow-Origin: * header to all requests, including the SSE connection, which allows any websites to send any request to the development server and read the response.
https://github.com/evanw/esbuild/blob/df815ac27b84f8b34374c9182a93c94718f8a630/pkg/api/serve_other.go#L121 https://github.com/evanw/esbuild/blob/df815ac27b84f8b34374c9182a93c94718f8a630/pkg/api/serve_other.go#L363
Attack scenario:
http://malicious.example.com).fetch('http://127.0.0.1:8000/main.js') request by JS in that malicious web page. This request is normally blocked by same-origin policy, but that's not the case for the reasons above.http://127.0.0.1:8000/main.js.In this scenario, I assumed that the attacker knows the URL of the bundle output file name. But the attacker can also get that information by
/index.html: normally you have a script tag here/assets: it's common to have a assets directory when you have JS files and CSS files in a different directory and the directory listing feature tells the attacker the list of files/esbuild SSE endpoint: the SSE endpoint sends the URL path of the changed files when the file is changed (new EventSource('/esbuild').addEventListener('change', e => console.log(e.type, e.data)))The scenario above fetches the compiled content, but if the victim has the source map option enabled, the attacker can also get the non-compiled content by fetching the source map file.
npm inpm run watchfetch('http://127.0.0.1:8000/app.js').then(r => r.text()).then(content => console.log(content)) in a different website's dev tools.Users using the serve feature may get the source code stolen by malicious websites.