This PR contains the following updates:

Package	Change	Age	Confidence
esbuild	0.28.0 → 0.28.1

esbuild enables any website to send any requests to the development server and read the response

GHSA-67mh-4wv8-2f99

Details

Summary

esbuild allows any websites to send any request to the development server and read the response due to default CORS settings.

Details

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:

1. The attacker serves a malicious web page (http://malicious.example.com).
2. The user accesses the malicious web page.
3. The attacker sends a 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.
4. The attacker gets the content of 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

• Fetching /index.html: normally you have a script tag here
• Fetching /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
• Connecting /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)))
• Fetching URLs in the known file: once the attacker knows one file, the attacker can know the URLs imported from that file

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.

PoC

1. Download reproduction.zip
2. Extract it and move to that directory
3. Run npm i
4. Run npm run watch
5. Run fetch('http://127.0.0.1:8000/app.js').then(r => r.text()).then(content => console.log(content)) in a different website's dev tools.

Impact

Users using the serve feature may get the source code stolen by malicious websites.

Severity

• CVSS Score: 5.3 / 10 (Medium)
• Vector String: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N

References

• https://github.com/evanw/esbuild/security/advisories/GHSA-67mh-4wv8-2f99
• https://github.com/evanw/esbuild/commit/de85afd65edec9ebc44a11e245fd9e9a2e99760d
• https://github.com/advisories/GHSA-67mh-4wv8-2f99

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

esbuild allows arbitrary file read when running the development server on Windows

GHSA-g7r4-m6w7-qqqr

Details

Summary

The development server contains a path traversal vulnerability on Windows when serving files from servedir.

Due to the use of path.Clean() (which only normalizes forward-slash / separators) instead of a Windows-aware path normalization function, it is possible to craft requests using backslashes (\) that bypass the intended directory containment logic. An attacker can escape the configured servedir root and access arbitrary files on the filesystem.
This issue affects Windows environments only.

Details

The request path is sanitized using:

// https://github.com/evanw/esbuild/blob/v0.27.3/pkg/api/serve_other.go#L165
queryPath := path.Clean(req.URL.Path)[1:]

However:

• path.Clean() is POSIX-style and only understands / (docs: https://pkg.go.dev/path#Clean)
• On Windows, \ is a valid path separator
• path.Clean() does not treat \ as a separator

Later, the server constructs the absolute path:

// https://github.com/evanw/esbuild/blob/v0.27.3/pkg/api/serve_other.go#L221
absPath := h.fs.Join(h.servedir, queryPath)

If queryPath contains sequences such as:

..\..\..\..\..\..\..\Windows\system.ini

path.Clean() will not normalize them, but the Windows filesystem will interpret \ as directory separators when resolving absPath.
Because the implementation does not verify that the final resolved path remains within servedir, it allows directory traversal outside the intended root directory.

Vulnerable Code

// https://github.com/evanw/esbuild/blob/v0.27.3/pkg/api/serve_other.go#L165
	queryPath := path.Clean(req.URL.Path)[1:]
	....
	// Check for a file in the "servedir" directory
	if h.servedir != "" && kind != fs.FileEntry {
		absPath := h.fs.Join(h.servedir, queryPath)
		if absDir := h.fs.Dir(absPath); absDir != absPath {
			if entries, err, _ := h.fs.ReadDirectory(absDir); err == nil {
				if entry, _ := entries.Get(h.fs.Base(absPath)); entry != nil && entry.Kind(h.fs) == fs.FileEntry {
	....				

Steps to reproduce

npm install --save-exact --save-dev esbuild

echo "console.log(1)" > app.js

.\node_modules\.bin\esbuild --version
0.27.3

.\node_modules\.bin\esbuild app.js --bundle --outdir=www --servedir=www --watch

curl -i --path-as-is "http://localhost:8000/..\..\..\..\..\..\..\Windows\system.ini"
<content of Windows\system.ini>

Impact

• Arbitrary file read on Windows
• Exposure of sensitive files

Severity

• CVSS Score: 2.5 / 10 (Low)
• Vector String: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N

References

• https://github.com/evanw/esbuild/security/advisories/GHSA-g7r4-m6w7-qqqr
• https://github.com/evanw/esbuild/releases/tag/v0.28.1
• https://github.com/advisories/GHSA-g7r4-m6w7-qqqr

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

Release Notes

v0.28.1

Compare Source

• Disallow \ in local development server HTTP requests (GHSA-g7r4-m6w7-qqqr)

  This release fixes a security issue where HTTP requests to esbuild's local development server could traverse outside of the serve directory on Windows using a \ backslash character. It happened due to the use of Go's path.Clean() function, which only handles Unix-style / characters. HTTP requests with paths containing \ are no longer allowed.

  Thanks to @​dellalibera for reporting this issue.

• Add integrity checks to the Deno API (GHSA-gv7w-rqvm-qjhr)

  The previous release of esbuild added integrity checks to esbuild's npm install script. This release also adds integrity checks to esbuild's Deno install script. Now esbuild's Deno API will also fail with an error if the downloaded esbuild binary contains something other than the expected content.

  Note that esbuild's Deno API installs from registry.npmjs.org by default, but allows the NPM_CONFIG_REGISTRY environment variable to override this with a custom package registry. This change means that the esbuild executable served by NPM_CONFIG_REGISTRY must now match the expected content.

  Thanks to @​sondt99 for reporting this issue.

• Avoid inlining using and await using declarations (#​4482)

  Previously esbuild's minifier sometimes incorrectly inlined using and await using declarations into subsequent uses of that declaration, which then fails to dispose of the resource correctly. This bug happened because inlining was done for let and const declarations by avoiding doing it for var declarations, which no longer worked when more declaration types were added. Here's an example:

  // Original code
  {
    using x = new Resource()
    x.activate()
  }
  
  // Old output (with --minify)
  new Resource().activate();
  
  // New output (with --minify)
  {using e=new Resource;e.activate()}

• Fix module evaluation when an error is thrown (#​4461, #​4467)

  If an error is thrown during module evaluation, esbuild previously didn't preserve the state of the module for subsequent module references. This was observable if import() or require() is used to import a module multiple times. The thrown error is supposed to be thrown by every call to import() or require(), not just the first. With this release, esbuild will now throw the same error every time you call import() or require() on a module that throws during its evaluation.

• Fix some edge cases around the new operator (#​4477)

  Previously esbuild incorrectly printed certain edge cases involving complex expressions inside the target of a new expression (specifically an optional chain and/or a tagged template literal). The generated code for the new target was not correctly wrapped with parentheses, and either contained a syntax error or had different semantics. These edge cases have been fixed so that they now correctly wrap the new target in parentheses. Here is an example of some affected code:

  // Original code
  new (foo()`bar`)()
  new (foo()?.bar)()
  
  // Old output
  new foo()`bar`();
  new (foo())?.bar();
  
  // New output
  new (foo())`bar`();
  new (foo()?.bar)();

• Fix renaming of nested var declarations (#​4471)

  This release fixes a bug where var declarations in nested scopes that are hoisted up to module scope were not correctly being renamed during bundling. That could previously lead to name collisions when minification was disabled, which could potentially cause a behavior change. The bug has been fixed so that these hoisted declarations are now considered to be module-level symbols during the name collision avoidance pass.

• Emit var instead of const for certain TypeScript-only constructs for ES5 (#​4448)

  While esbuild doesn't generally support converting const to var for ES5 due to nested scoping rules (which is currently a build-time error), esbuild previously incorrectly converted TypeScript-only import assignment constructs into a const declaration even when targeting ES5. With this release, esbuild will now use var for this case instead:

  // Original code
  import x = require('y')
  
  // Old output (with --target=es5)
  const x = require("y");
  
  // New output (with --target=es5)
  var x = require("y");

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