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CVE-2025-66478 — Next.js Remote Code Execution

Key facts

CVE-2025-66478 is a Critical (10.0) vulnerability: Next.js Remote Code Execution. This entry ships a detection-only PoC.
CVE CVE-2025-66478
Severity Critical (10.0)
Detection / prevention —
PoC poc.py
Source 2025/CVE-2025-66478/

Details

CVSS Type

Overview

Attribute Value
CVE ID CVE-2025-66478
Severity Critical
CVSS Score 10.0
Affected Product Next.js
Vulnerability Type Remote Code Execution
CWE CWE-502

Description

CVE assigned for React2Shell vulnerability (CVE-2025-55182) as it impacts Next.js applications using App Router. 39% of cloud environments contain vulnerable instances.

Affected Versions

  • Next.js with App Router using Server Actions

Verification Process

The PoC uses a multi-stage verification approach:

Step 1: Product/Version Detection (Passive)

[*] Query target endpoint
[*] Detect product signatures and extract version
[*] Check if version is in vulnerable range

Step 2: Active Vulnerability Testing

Method Description Detection
Error-based Inject payloads that trigger error messages Error indicators in response
Timing-based Inject delay commands and measure response Response time > baseline + delay
Response-based Check for expected patterns in response Pattern match in response body
Callback-based Trigger OOB request to attacker server HTTP request received

Verification Flow

┌─────────────────────────────────────────────────────────────┐
│                    Product Detection                         │
│  Query target → Detect product/version                      │
│  Check if version in vulnerable range                       │
└─────────────────────────────────────────────────────────────┘
                              ↓
┌─────────────────────────────────────────────────────────────┐
│               Active Vulnerability Testing                   │
│                                                              │
│  1. Error-based Test                                         │
│     └─ Send payload → Check for error indicators            │
│     └─ If error found → CONFIRMED VULNERABLE                │
│                                                              │
│  2. Timing-based Test                                        │
│     └─ Send delay payload → Measure response time           │
│     └─ If delayed → CONFIRMED VULNERABLE                    │
│                                                              │
│  3. Callback-based Test (if URL provided)                    │
│     └─ Send OOB payload → Check callback server             │
│     └─ If request received → CONFIRMED VULNERABLE           │
└─────────────────────────────────────────────────────────────┘

Usage

# Full vulnerability check (version + active testing)
python3 poc.py -t https://target.com -c

# Version-only check (passive, no payloads sent)
python3 poc.py -t https://target.com -c --version-only

# With OOB callback (most reliable)
python3 poc.py -t https://target.com -c --callback http://your-server.com

Mitigation

  1. Upgrade to the latest patched version
  2. Apply workarounds if patch unavailable
  3. Monitor for exploitation attempts
  4. Network segmentation to limit exposure

References

Frequently asked questions

What is CVE-2025-66478?

CVE-2025-66478 is a Critical (10.0) vulnerability: Next.js Remote Code Execution. This entry ships a detection-only PoC.

How do I detect CVE-2025-66478?

Run the detection-only PoC included with this entry against your Docker test lab to confirm whether a target is affected; pair it with your own IDS logging.

How do I block or mitigate CVE-2025-66478?

Upgrade to a fixed version per the vendor advisory; the NVD record lists the affected versions. Use the included PoC to verify your remediation.

For authorized security testing and research only. See the full source and NVD record.