What is the CVSS score of CVE-2026-27977?

CVE-2026-27977 has a CVSS 3.1 base score of 5.4 (Medium). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N. EPSS exploitation probability: 0.0%.

How to fix or mitigate CVE-2026-27977?

Within 30 days: Identify affected systems and apply vendor patches as part of regular patch cycle. Vendor patch is available.

Red Hat CVE-2026-27977

MEDIUM

Missing Origin Validation in WebSockets (CWE-1385)

2026-03-17 https://github.com/vercel/next.js

GHSA-jcc7-9wpm-mj36

Information Disclosure Red Hat

5.4

CVSS 3.1 · GitHub Advisory

View

Vulnerability Assessment

Weakness	CWE CWE-1385 OWASP Top 10:2025 A06:2021 - Vulnerable and Outdated Components ASVS 5.0 V15 - Secure Coding and Architecture Hardware safety mechanism
Impact	CVSS 5.4. EPSS 0.0%. Vendor patch available.
Exploit ScenarioDerived	An attacker could exploit this vulnerability in the affected application to compromise the security of affected deployments, potentially impacting confidentiality, integrity, or availability.

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).

Patch available 0.0% exploitation probability (EPSS)

Get an e-mail when this CVE is exploited, patched or re-scored. Free account.

Alert me

AnalysisAIv1 – Mar 17, 2026

CVE-2026-27977 is a security vulnerability (CVSS 5.4). Remediation should follow standard vulnerability management procedures. Vendor patch is available.

Earlier versions of this analysis (1)

v1 Mar 17, 2026 - 20:30 CVSS 5.4

In next dev, cross-site protection for internal websocket endpoints could treat Origin: null as a bypass case even if [allowedDevOrigins](https://nextjs.org/docs/app/api-reference/config/next-co

RemediationAI

Apply the vendor-supplied patch immediately.

Affected Packages

npm next fix: 16.1.7

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in npm

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

Vulnerability type not specified by vendor.

Know when the next one hits your stack

Watch products and get an email when something new is published
Check this CVE against your own stack and servers
Exploit and PoC references, threat intelligence from 22 sources

Continue with Google Continue with GitHub

No credit card · 7-day full trial

Severity by source

GitHub Advisory PRIMARY 5.4 MEDIUM

AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N

Red Hat 4.2 MEDIUM

Primary rating from GitHub Advisory.

CVSS VectorGitHub Advisory

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

Required

Scope

Unchanged

Confidentiality

Low

Integrity

Low

Availability

None

Lifecycle Timeline

Patch released

Mar 17, 2026 - 20:30 nvd

Patch available

CVE Published

Mar 17, 2026 - 15:29 nvd

MEDIUM 5.4

DescriptionGitHub Advisory

Summary

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.

Impact

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.

Patches

Fixed by validating Origin: null through the same cross-site origin-allowance checks used for other origins.

Workarounds

If upgrade is not immediately possible:

Do not expose next dev to untrusted networks.
Block websocket upgrades to /_next/webpack-hmr when Origin is null at your proxy.

Executive ViewAI

Why It Matters

CVE-2026-27977 presents moderate security risk rated CVSS 5.4. Exploitation could compromise the security of affected deployments. A patch is available and should be applied during regular vulnerability management.

Business Impact: Low

Compensating Controls

Apply vendor patch. If patching is delayed: restrict network access and enable monitoring.

Threat Intelligence Overview

EPSS Score

0.0%

Top 96% exploitable

Data Quality

5 sources

Confidence: Medium

NVD

CVE.org

EPSS Vendor

GitHub

VulDB

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity MEDIUM

CISA KEV No

Public POC No

EPSS 0.0%

Patch available Yes

Active threat No

Deciding rule

MEDIUM severity (CVSS 4.0-6.9)

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived

Defer

Exploitation· derived

None

System Exposure· derived

Open

Automatable· derived

Human Impact

Low

Priority Score

Low Medium High Critical

KEV: 0

EPSS: 0

CVSS: +27

PoC: 0

Weaponized: 0

Threat intel: 0

Gov advisory: 0

Attack Technique

Information Disclosure MEDIUM

Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.