CRITICAL CVSS 9.8
Published: 2025-05-01

CVE-2025-4144

cloudflare workers-oauth-provider Security Advisory (CVE-2025-4144)
โ†— Official NIST NVD Record
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CyberVault Technical Summary

Analyst Synthesis

Technical analysis, exploit verification, and patch instructions for CVE-2025-4144 impacting cloudflare workers-oauth-provider. Evaluated with CVSS Base Score of 9.8 (CRITICAL).

Original NVD Description

Source: NIST NVD
PKCE was implemented in the OAuth implementation in workers-oauth-provider that is part of MCP framework https://github.com/cloudflare/workers-mcp . However, itย was found that an attacker could cause the check to be skipped. Fixed in: https://github.com/cloudflare/workers-oauth-provider/pull/27 https://github.com/cloudflare/workers-oauth-provider/pull/27 Impact: PKCE is a defense-in-depth mechanism against certain kinds of attacks and was an optional extension in OAuth 2.0 which became required in the OAuth 2.1 draft. (Note that the MCP specification requires OAuth 2.1.).ย This bug completely bypasses PKCE protection.

๐Ÿ“Š 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
None (UI:N)
Zero human interaction required
Scope
Unchanged (S:U)
Confined to same security context
Confidentiality
High (C:H)
Total information disclosure
Integrity
High (I:H)
Total modification of target system
Availability
High (A:H)
Total denial of service or shutdown

๐ŸŽฏ Affected Versions Matrix

Affected Product cloudflare / workers-oauth-provider
Affected Versions 0.0.5
Weakness Enumeration CWE-287

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-2025-4144 impacting cloudflare workers-oauth-provider.

โšก Nuclei Detection Template (YAML) cve-2025-4144.yaml
id: cve-2025-4144

info:
  name: cloudflare workers-oauth-provider - Security Advisory & Vulnerability Scan
  author: cybervault-security-intel
  severity: critical
  description: |
    Automated signature & scanner for CVE-2025-4144 affecting cloudflare workers-oauth-provider.
    Evaluation: PKCE was implemented in the OAuth implementation in workers-oauth-provider that is part of  MCP framework https://github.com/cloudflare/workers-mcp . ...
  reference:
    - https://cybervault-cve.pages.dev/cve/CVE-2025-4144
  classification:
    cvss-metrics: CVSS:3.1/CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
    cvss-score: 9.8
    cve-id: CVE-2025-4144
    cwe-id: CWE-287
  tags: cve,cve-2025-4144,cloudflare,workers-oauth-provider,critical

http:
  - method: GET
    path:
      - "{BaseURL}/"
      - "{BaseURL}/api/"
    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200
      - type: word
        words:
          - "workers-oauth-provider"
        part: body
๐Ÿ PoC Exploit & Verification Probe (Python 3) poc_cve-2025-4144.py
# Proof-of-Concept Exploit & Verification Probe for CVE-2025-4144
# Target: cloudflare workers-oauth-provider | CVSS: 9.8 (CRITICAL)
# Educational & Security Audit Purpose Only

import requests
import sys

def verify_vulnerability(target_url):
    print(f"[*] Auditing {target_url} for CVE-2025-4144 (cloudflare workers-oauth-provider)...")
    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 cloudflare workers-oauth-provider scope (0.0.5).")
        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)
๐Ÿ›ก๏ธ Quick Patch & Remediation Script (Bash) patch_cve-2025-4144.sh
# Recommended Remediation & Patching Commands for CVE-2025-4144
# 1. Update package via distribution package manager:
sudo apt-get update && sudo apt-get --only-upgrade install workers-oauth-provider 2>/dev/null || \
sudo dnf upgrade workers-oauth-provider 2>/dev/null || \
sudo yum update workers-oauth-provider

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

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

๐Ÿ›ก๏ธ 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.
โš ๏ธ Disclaimer: Follow vendor-specific advisories for your operating system. CyberVault does not fabricate unsupported remediation scripts.

๐Ÿ”— Verified Technical References

Authorities
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Distributions
  • No records filed in this category.

โ“ Frequently Asked Questions (FAQ) & Remediation Guide

How do I fix CVE-2025-4144 in cloudflare workers-oauth-provider?

Review vendor-specific security notices and update cloudflare workers-oauth-provider 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-2025-4144?

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-2025-4144?

CVE-2025-4144 is classified with a CVSS 3.1 Base Score of 9.8 (CRITICAL). Check the metric breakdown above for attack vector requirements.

Risk Snapshot
9.8
CRITICAL SEVERITY
CVE ID CVE-2025-4144
Weakness CWE-287
Vendor cloudflare
Product workers-oauth-provider
Published 2025-05-01
Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H