CVE-2025-59427

Executive Summary

CVE-2025-59427 is a critical information disclosure vulnerability in the Cloudflare Vite plugin, which integrates Vite with the Workers runtime. In its default configuration, the local development server exposes all files in the root directory, including sensitive files such as .env and .dev.vars. This allows an attacker to access secret information like API keys, tokens, and environment variables. The vulnerability is fixed in version 1.6.0.

Supply Chain & Package Security

This vulnerability affects the npm package @cloudflare/vite-plugin. Users of this package are at risk if they are using a version prior to 1.6.0. The exposure of .env and .dev.vars files can lead to credential theft and further compromise of Cloudflare Workers and associated services.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (No official CVSS vector provided)
• Attack Vector: Network (local dev server)
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: None
• Scope: Unchanged
• Confidentiality Impact: High
• Integrity Impact: None
• Availability Impact: None
• Threat Level: High (due to ease of exploitation and potential for credential theft)

Deep Dive & Mechanics

The Cloudflare Vite plugin, when used in its default configuration, does not properly restrict file access on the local development server. The Vite dev server, by design, serves static files from the project root. However, the plugin fails to exclude sensitive files like .env and .dev.vars from being served. An attacker who can access the local dev server (e.g., via a network request or by tricking a developer into visiting a malicious link) can retrieve these files.

The vulnerability is rooted in the plugin's configuration, which does not implement a deny list for sensitive files. The fix in version 1.6.0 likely adds such a deny list or modifies the server configuration to prevent serving these files.

Vulnerable vs. Patched Code

Vulnerable Code (pre-1.6.0): The plugin's configuration likely uses a default Vite server setup without any file exclusion rules. For example:

// vulnerable configuration
export default defineConfig({
  plugins: [cloudflare()],
  server: {
    // no deny list for sensitive files
  }
});

Patched Code (1.6.0): The patched version adds a deny list or modifies the server middleware to block access to sensitive files. For example:

// patched configuration
export default defineConfig({
  plugins: [cloudflare()],
  server: {
    fs: {
      deny: ['.env', '.dev.vars', '**/.env*']
    }
  }
});

Exploitation & Lab Setup

Red Team

1. Setup: Install a vulnerable version of the Cloudflare Vite plugin (e.g., 1.5.0) and create a project with a .env file containing test credentials.
2. Exploit: Access the local dev server (default http://localhost:5173) and request the .env file directly:

   curl http://localhost:5173/.env
   

   This will return the contents of the .env file.
3. Automation: Use a script to enumerate common sensitive files:

   for file in .env .dev.vars .env.local .env.production; do
     curl -s -o /dev/null -w "%{http_code}" http://localhost:5173/$file
   done
   

Blue Team

1. Detection: Monitor for requests to sensitive files on the dev server. Use the Sigma rule provided in the Detection Engineering section.
2. Mitigation: Immediately upgrade to version 1.6.0 or later. If upgrade is not possible, manually configure the Vite server to deny access to sensitive files:

   export default defineConfig({
     server: {
       fs: {
         deny: ['.env', '.dev.vars', '**/.env*']
       }
     }
   });
   

3. Network Segmentation: Ensure the dev server is not exposed to the internet or untrusted networks. Use firewall rules to restrict access to localhost only.

Indicators of Compromise (IOCs)

• File Access: Unauthorized access to .env, .dev.vars, or other sensitive files on the Vite dev server.
• Network Traffic: HTTP GET requests to paths like /.env, /.dev.vars, /config/.env on the dev server port (default 5173).
• Logs: Vite dev server logs showing 200 responses for sensitive file requests.

Detection Engineering

YARA Rule

rule CVE_2025_59427_Cloudflare_Vite_Plugin {
  meta:
    description = "Detects attempts to exploit CVE-2025-59427 by accessing sensitive files on Vite dev server"
    author = "Valters IT"
    date = "2025-04-10"
    reference = "CVE-2025-59427"
  strings:
    $sensitive_file = ".env" nocase
    $dev_vars = ".dev.vars" nocase
    $vite_server = "Vite" nocase
  condition:
    any of ($sensitive_file, $dev_vars) and $vite_server
}

Sigma Rule

title: CVE-2025-59427 - Cloudflare Vite Plugin Sensitive File Access
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects HTTP requests to sensitive files on a Vite dev server
author: Valters IT
date: 2025-04-10
logsource:
  category: webserver
  product: vitedev
detection:
  selection:
    cs-method: 'GET'
    cs-uri-stem:
      - '/.env'
      - '/.dev.vars'
      - '/.env.local'
      - '/.env.production'
  condition: selection
falsepositives:
  - Legitimate development activities (rare)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-59427 - Cloudflare Vite Plugin Sensitive File Access"; flow:to_server; content:"GET"; http_method; content:".env"; http_uri; nocase; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate Action: Upgrade the Cloudflare Vite plugin to version 1.6.0 or later.
2. Workaround: If upgrade is not possible, manually configure the Vite server to deny access to sensitive files:

   export default defineConfig({
     server: {
       fs: {
         deny: ['.env', '.dev.vars', '**/.env*']
       }
     }
   });
   

3. Network Security: Ensure the dev server is only accessible from localhost. Use firewall rules to block external access to the dev server port.
4. Credential Rotation: If any sensitive files were exposed, rotate all credentials and secrets immediately.
5. Monitoring: Implement the detection rules provided in this report to monitor for exploitation attempts.

Valters IT
DevSecOps & Cyber Threat Intelligence Expert