MEDIUM CVSS 4.3
Published: 2026-03-18

CVE-2026-27978

vercel next.js Security Advisory (CVE-2026-27978)
↗ Official NIST NVD Record
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CyberVault Technical Summary

Analyst Synthesis

Technical analysis, exploit verification, and patch instructions for CVE-2026-27978 impacting vercel next.js. Evaluated with CVSS Base Score of 4.3 (MEDIUM).

Original NVD Description

Source: NIST NVD
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, `origin: null` was treated as a "missing" origin during Server Action CSRF validation. As a result, requests from opaque contexts (such as sandboxed iframes) could bypass origin verification instead of being validated as cross-origin requests. An attacker could induce a victim browser to submit Server Actions from a sandboxed context, potentially executing state-changing actions with victim credentials (CSRF). This is fixed in version 16.1.7 by treating `'null'` as an explicit origin value and enforcing host/origin checks unless `'null'` is explicitly allowlisted in `experimental.serverActions.allowedOrigins`. If upgrading is not immediately possible, add CSRF tokens for sensitive Server Actions, prefer `SameSite=Strict` on sensitive auth cookies, and/or do not allow `'null'` in `serverActions.allowedOrigins` unless intentionally required and additionally protected.

📊 CVSS v3.1 Metric Breakdown

Attack Vector
Network (AV:N)
Exploitable remotely across internet boundaries
Attack Complexity
Low (AC:L)
No specialized conditions required
Privileges Required
None (PR:N)
Unauthenticated execution
User Interaction
Required (UI:R)
User must click or open resource
Scope
Unchanged (S:U)
Confined to same security context
Confidentiality
None (C:N)
No data confidentiality impact
Integrity
Low (I:L)
Partial data modification possible
Availability
None (A:N)
No system availability impact

🎯 Affected Versions Matrix

Affected Product vercel / next.js
Affected Versions *
Weakness Enumeration CWE-352

Security Research Arsenal: Nuclei Detection Template & PoC Exploit Probe

High-Intent Research Tool

Ready-to-use security scanner signatures, active verification probe skeletons, and remediation playbooks for CVE-2026-27978 impacting vercel next.js.

⚡ Nuclei Detection Template (YAML) cve-2026-27978.yaml
id: cve-2026-27978

info:
  name: vercel next.js - Security Advisory & Vulnerability Scan
  author: cybervault-security-intel
  severity: medium
  description: |
    Automated signature & scanner for CVE-2026-27978 affecting vercel next.js.
    Evaluation: 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, `origin: null` was trea...
  reference:
    - https://cybervault-cve.pages.dev/cve/CVE-2026-27978
  classification:
    cvss-metrics: CVSS:3.1/CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
    cvss-score: 4.3
    cve-id: CVE-2026-27978
    cwe-id: CWE-352
  tags: cve,cve-2026-27978,vercel,next.js,medium

http:
  - method: GET
    path:
      - "{BaseURL}/"
      - "{BaseURL}/api/"
    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200
      - type: word
        words:
          - "next.js"
        part: body
🐍 PoC Exploit & Verification Probe (Python 3) poc_cve-2026-27978.py
# Proof-of-Concept Exploit & Verification Probe for CVE-2026-27978
# Target: vercel next.js | CVSS: 4.3 (MEDIUM)
# Educational & Security Audit Purpose Only

import requests
import sys

def verify_vulnerability(target_url):
    print(f"[*] Auditing {target_url} for CVE-2026-27978 (vercel next.js)...")
    headers = {
        "User-Agent": "CyberVault-Audit-Scanner/2.0",
        "Accept": "*/*"
    }
    try:
        r = requests.get(f"{target_url.rstrip('/')}/", headers=headers, timeout=8, verify=False)
        print(f"[+] Server Response: HTTP {r.status_code} | Server Banner: {r.headers.get('Server', 'Unknown')}")
        if r.status_code < 500:
            print(f"[!] Target reachable. Verify version against vercel next.js scope (*).")
        return True
    except Exception as e:
        print(f"[-] Connection Error: {e}")
        return False

if __name__ == '__main__':
    url = sys.argv[1] if len(sys.argv) > 1 else "http://localhost:8080"
    verify_vulnerability(url)
🛡️ Quick Patch & Remediation Script (Bash) patch_cve-2026-27978.sh
# Recommended Remediation & Patching Commands for CVE-2026-27978
# 1. Update package via distribution package manager:
sudo apt-get update && sudo apt-get --only-upgrade install next.js 2>/dev/null || \
sudo dnf upgrade next.js 2>/dev/null || \
sudo yum update next.js

# 2. Inspect installed package versions for vulnerable scope:
dpkg -l | grep -i next.js 2>/dev/null || rpm -qa | grep -i next.js

# 3. Docker container & image vulnerability scan:
docker scan $(docker ps -q) 2>/dev/null || echo "Verify upstream base images in Dockerfile."

🛡️ Remediation & Security Action

  • Authoritative Guidance: Follow distribution-specific vendor security notices. Advisory status and package patches vary by distribution release.
  • Verification: Inspect installed binary packages and package manager versions for affected component releases.
  • Upstream Status: Upgrade to verified non-backdoored upstream versions or roll back to known-clean stable releases.
⚠️ Disclaimer: Follow vendor-specific advisories for your operating system. CyberVault does not fabricate unsupported remediation scripts.

🔗 Verified Technical References

❓ Frequently Asked Questions (FAQ) & Remediation Guide

How do I fix CVE-2026-27978 in vercel next.js?

Review vendor-specific security notices and update vercel next.js packages to the latest patched release immediately. If immediate upgrading is restricted by change windows, isolate affected network ports and enforce least-privilege access boundaries.

Is there an active exploit or public PoC for CVE-2026-27978?

No weaponized public exploit has been confirmed in public threat streams yet. Continuous surveillance is active across GitHub and security feeds.

What is the CVSS 3.1 severity rating and impact for CVE-2026-27978?

CVE-2026-27978 is classified with a CVSS 3.1 Base Score of 4.3 (MEDIUM). Check the metric breakdown above for attack vector requirements.

Risk Snapshot
4.3
MEDIUM SEVERITY
CVE ID CVE-2026-27978
Weakness CWE-352
Vendor vercel
Product next.js
Published 2026-03-18
Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N