Esbuild, a blazing-fast JavaScript and CSS bundler, released version 0.14.26 shortly after 0.14.25. Comparing these releases reveals a straightforward dependency update across the supported platforms. Both versions bundle the core esbuild package with specific binary packages tailored to various operating systems and architectures. These include esbuild-linux-64, esbuild-darwin-64, esbuild-windows-64, and numerous others spanning Linux (x32, x64, ARM, ARM64, s390x, ppc64le, riscv64, mips64le), macOS (x64, ARM64), Windows (x32, x64, ARM64), SunOS, NetBSD, Android, FreeBSD and OpenBSD. Each platform receives its own optimized binary for maximum performance.
The key difference lies in the version number of these dependencies; version 0.14.26 uses 0.14.26 of the platform-specific binaries, while v0.14.25 utilizes 0.14.25. This implies that the newer release likely includes bug fixes, performance improvements, or feature enhancements within the core esbuild engine that necessitate an update to the bundled binaries. Developers should upgrade to the latest version to benefit from the most recent improvements and potentially address any bugs present in the previous release. Both versions maintain the MIT license, ensuring flexibility for various project types and the repository URL remains the same. Also filecount and unpacked size did not change and stay at 6 and 117579 respectively.
All the vulnerabilities related to the version 0.14.26 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.