Esbuild 0.14.40 represents a minor version update to the lightning-fast JavaScript and CSS bundler, building upon the solid foundation of 0.14.39. The core functionality and primary goal of extreme speed remain consistent, targeting developers who demand rapid build times for their projects. Examining the package data reveals a consistent structure, with both versions declaring identical dependencies and optional dependencies, all mirroring the parent package version. This architectural choice ensures platform-specific builds are readily available for a wide array of operating systems and architectures, ranging from Linux (x32, x64, ARM, ARM64, s390x, ppc64le, riscv64, mips64le) to Windows (x32, x64, ARM64), macOS (x64, ARM64), and even more specialized platforms like SunOS, NetBSD, Android, FreeBSD and OpenBSD.
The most notable change lies in the releaseDate. Version 0.14.40 was published on May 27, 2022, while 0.14.39 was released on May 11, 2022. This indicates a relatively quick turnaround between these two versions. Although the metadata provides no immediate details of changes in functionality, developers should refer to the official esbuild changelog or release notes for a comprehensive understanding of bug fixes, performance improvements, or new features introduced in version 0.14.40. Therefore, while the architecture ensures continued wide platform support, developers should investigate the updates behind the release date to take advantage of the latest improvements or potential bug fixes.
All the vulnerabilities related to the version 0.14.40 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.