Esbuild version 0.14.34 represents a minor update to the popular JavaScript and CSS bundler and minifier, building upon the solid foundation established by version 0.14.33. Examining the package metadata reveals that the core functionality and purpose remain consistent: providing an extremely fast build tool for web development workflows. The primary difference lies in the versions of its platform-specific dependencies, such as esbuild-linux-64, esbuild-windows-64, and others. These dependencies, essential for running esbuild on various operating systems and architectures, have been bumped from version 0.14.33 to 0.14.34 to ensure compatibility and potentially incorporate bug fixes or performance improvements tailored to each platform.
From a developer's perspective, this update signifies a maintenance release. While significant new features or API changes are unlikely, upgrading from 0.14.33 to 0.14.34 is advisable to benefit from the latest platform-specific optimizations and bug fixes, ensuring a stable and performant build process. Given the minimal scope of the changes, the upgrade process should be straightforward and should not require any code modifications in most cases. Developers should always consult the official esbuild changelog for detailed information on the specific changes included in each release and any potential breaking changes. This minor version bump ensures the continued reliability and performance that developers have come to expect from esbuild.
All the vulnerabilities related to the version 0.14.34 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.