`nx graph` dev server permissive CORS policy

Summary

The local HTTP server started by nx graph sent Access-Control-Allow-Origin: * on every response, letting any website a developer visited read the server's responses cross-origin — including the full project graph and the output of the /help endpoint, which runs a target's configured help command. The practical impact is typically cross-origin information disclosure, but can be arbitrary command injection in rare cases.

Severity

Exploitation requires the developer to be running nx graph and to visit an attacker page. Any execution beyond benign help commands also requires a malicious target to already be present in the workspace (see Details).

Affected & Patched Versions

Package: nx (npm).

• Affected: >= 17.0.4, < 22.7.2 and >= 23.0.0-beta.0, < 23.0.0-beta.2
• Patched: 22.7.2+ (backport) and 23.0.0 (first in 23.0.0-beta.2)

The wildcard CORS header was introduced in 17.0.4; the /help execution endpoint in 19.4.0. The 21.x line is not patched — 21.x users should upgrade to 22.7.2 or later.

Details

nx graph starts a local server (default http://127.0.0.1:4211). Before the fix, its request handler set a wildcard CORS header on every response:

res.setHeader('Access-Control-Allow-Origin', '*');

The /help endpoint runs a target's configured command:

const command = target.metadata?.help?.command;
return execSync(command, { cwd: target.options?.cwd ?? workspaceRoot }).toString();

A GET /help is a CORS "simple request", so a malicious page could fetch() it with no preflight, and the wildcard header let the page read the result. This exposes the project graph (project names, file paths, dependencies, build configuration) and the output of any configured help command.

The command is not attacker-controlled through the request — it comes from the workspace's project configuration, and first-party plugins (jest, vite, cypress) populate it with benign, read-only help commands. For /help to run anything malicious, a target carrying a malicious help.command must already exist in the project graph, which can only be introduced by installing a malicious package or by altering the workspace's own code/configuration — both of which already grant code execution independent of this flaw.

The fix (#35494) removes the header; the browser's same-origin policy then blocks cross-origin reads.

References

• Fix: nrwl/nx#35494
• Introduced: nrwl/nx#20744 (CORS), nrwl/nx#26629 (/help)

Credits

Thanks to Nozomu Sasaki (Paul) (@morimori-dev) for finding and responsibly reporting this issue.