Description
Next.js is a React framework for building full-stack web applications. Starting in version 16.0.1 and prior to version 16.1.7, in `next dev`, cross-site protection for internal websocket endpoints could treat `Origin: null` as a bypass case even if `allowedDevOrigins` is configured, allowing privacy-sensitive/opaque contexts (for example sandboxed documents) to connect unexpectedly. If a dev server is reachable from attacker-controlled content, an attacker may be able to connect to the HMR websocket channel and interact with dev websocket traffic. This affects development mode only. Apps without a configured `allowedDevOrigins` still allow connections from any origin. The issue is fixed in version 16.1.7 by validating `Origin: null` through the same cross-site origin-allowance checks used for other origins. If upgrading is not immediately possible, do not expose `next dev` to untrusted networks and/or block websocket upgrades to `/_next/webpack-hmr` when `Origin` is `null` at the proxy.
INFO
Published Date :
2026-03-17T23:56:24.631Z
Last Modified :
2026-03-18T19:56:16.843Z
Source :
GitHub_M
AFFECTED PRODUCTS
The following products are affected by CVE-2026-27977 vulnerability.
| Vendors | Products |
|---|---|
| Vercel |
|
REFERENCES
Here, you will find a curated list of external links that provide in-depth information to CVE-2026-27977.
