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%.

Which versions of Red Hat are affected by CVE-2026-27977?

CVE-2026-27977 presents moderate security risk rated CVSS 5.4. Exploitation could compromise the security of affected deployments.. A patch is available.

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

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

qualitative

Primary rating from GitHub Advisory.

CVSS VectorGitHub Advisory

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

Required

Scope

Unchanged

Confidentiality

Low

Integrity

Low

Availability

None

Lifecycle Timeline

Analysis Generated

Mar 17, 2026 - 20:30 vuln.today

Patch released

Mar 17, 2026 - 20:30 nvd

Patch available

CVE Published

Mar 17, 2026 - 15:29 nvd

MEDIUM 5.4

Blast Radius

ecosystem impact

† from your stack dependencies † transitive graph · vuln.today resolves 4-path depth

47 npm packages depend on next (45 direct, 2 indirect)

Ecosystem-wide dependent count for version 16.0.1.

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.

AnalysisAI

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