Esbuild, an extremely fast JavaScript and CSS bundler and minifier, has released a new version, 0.17.7, succeeding the previous stable version 0.17.6. The core functionality remains consistent, promising developers speedy builds for their web projects. A key observation is the consistent dependency structure. Both versions rely on a suite of platform-specific binary packages, such as @esbuild/linux-x64, @esbuild/win32-arm64, and @esbuild/darwin-arm64, covering a wide range of operating systems and architectures, from Linux and Windows to macOS and Android. Both versions list these platform-specific binaries as both dependencies and optional dependencies, ensuring that the appropriate binary can be installed based on the user's system.
The crucial distinction between the two versions lies in the version numbers of these dependencies. Version 0.17.7 updates all the platform-specific dependencies to version 0.17.7, while version 0.17.6 uses 0.17.6. This signifies that version 0.17.7 likely includes bug fixes, performance improvements, or new features within these platform-specific binaries. Developers should upgrade to 0.17.7 to benefit from these updates, potentially resolving issues or enhancing build performance on their target platforms. The release date indicates that version 0.17.7 was released shortly after 0.17.6, and it is more than likely that this version fixes some bug found on the previous one. The fileCount and unpackedSize in the dist object remained the same, which means that the core functionality of esbuild is consistent across both versions.
All the vulnerabilities related to the version 0.17.7 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.