---
cve: "CVE-2026-27977"
severity: "LOW"
cvss: 2.3
epss: "17%"
vendor: "vercel"
kev: false
exploited: false
published: "2026-03-18 00:16:19"
tags: [cve, security, low]
source: tsecurity.de CVE-Dossier
exported: "2026-09-13T17:08:57+02:00"
---

# CVE-2026-27977

> 2.3 LOW · 🧪 PoC

## Beschreibung

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.

## CVSS-Vektor

```
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N
```

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Gering | bad |
| PR Privilegien | Keine | bad |

## Patch verfügbar (OSV)

- bdf3e3577a6d55ea186a48238d61fbd8da07a626 (Commit)
- 862f9b9bb41d235e0d8cf44aa811e7fd118cee2a (Commit)

## Referenzen

- <https://github.com/vercel/next.js/security/advisories/GHSA-jcc7-9wpm-mj36>
- <https://github.com/vercel/next.js/commit/862f9b9bb41d235e0d8cf44aa811e7fd118cee2a>
- <https://github.com/vercel/next.js/releases/tag/v16.1.7>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-27977) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_