cvedb.io
CVE-2026-27977
MEDIUM · CVSS 5.4
EPSS exploitation probability: 0%
Published 2026-03-18T00:16:19.947 · Last modified 2026-06-17T10:28:00.327

Summary

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

Affected products

vercel — next.js

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References

This product uses data from the NVD API but is not endorsed or certified by the NVD. Informational only; not professional security advice.