Esbuild, a lightning-fast JavaScript and CSS bundler and minifier, has a new version, 0.14.36, released shortly after its predecessor, 0.14.35. While both versions share the same core functionality and description, the key difference lies in the specific versions of their platform-dependent dependencies. Both rely on a suite of optional and mandatory (but, duplicated) prebuilt binaries for various operating systems and architectures like Linux (32-bit, 64-bit, ARM, ARM64, s390x, ppc64le, riscv64, mips64le), macOS (64-bit, ARM64), Windows (32-bit, 64-bit, ARM64), Android (64-bit, ARM64), FreeBSD (64-bit, ARM64), NetBSD (64-bit), OpenBSD (64-bit), and SunOS (64-bit).
Version 0.14.36 updates these platform-specific esbuild-* packages to the 0.14.36 version, while version 0.14.35 carries the 0.14.35 versions of those. This means that while the core esbuild API remains consistent, developers might experience subtle bug fixes or performance improvements within the compiled binaries themselves when upgrading. While the core functionality and usage remain the same for both versions, developers should always consider upgrading to the latest patch release (in this case, 0.14.36) to benefit from the most recent fixes and optimizations within the platform-specific modules. Package size and other metadata remained identical. These quick releases are important and common as esbuild matures and caters to a wide variety of platforms and architectures.
All the vulnerabilities related to the version 0.14.36 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.