Insecure CORS Configuration in Fiber Middleware Framework

🚨 CRITICAL SECURITY ADVISORY

Insecure CORS Configuration in GoFiber Framework

CVE ID: GHSA-fmg4-x8pw-hjhg
Severity: CRITICAL
Published: February 21, 2024
Affected Package: github.com/gofiber/fiber/v2

📋 VULNERABILITY OVERVIEW

The GoFiber web framework contains a critical CORS (Cross-Origin Resource Sharing) middleware vulnerability that allows dangerous misconfigurations. The middleware permits setting wildcard origins (*) while simultaneously enabling credentials sharing, creating a severe security breach that violates CORS security standards.

🎯 AFFECTED VERSIONS

Vulnerable: All versions < 2.52.1
Patched: Versions >= 2.52.1
Components:
- github.com/gofiber/fiber/v2
- github.com/gofiber/fiber/v2/middleware/cors

⚠️ SECURITY IMPACT

Risk Level: HIGH to CRITICAL

This misconfiguration exposes applications to:

Unauthorized data access from any origin
Credential theft through malicious websites
Session hijacking attacks
Cross-site request forgery (CSRF) vulnerabilities
Data exfiltration from authenticated users

Any malicious website can now make credentialed requests to your application, bypassing the same-origin policy that protects users.

🔍 TECHNICAL DETAILS

The vulnerability exists in cors.go where the middleware fails to validate the dangerous combination of:

AllowOrigins: "*"
AllowCredentials: true

This configuration violates RFC specifications and security best practices, as browsers should reject such configurations but the middleware doesn’t prevent developers from creating them.

🛠️ IMMEDIATE ACTIONS REQUIRED

1. UPDATE IMMEDIATELY

go get github.com/gofiber/fiber/v2@latest

2. AUDIT YOUR CORS CONFIGURATION Review all CORS middleware implementations for:

Wildcard origins with credentials enabled
Overly permissive origin lists
Missing validation logic

3. TEMPORARY WORKAROUND (if immediate update isn’t possible) Manually validate CORS settings in your application:

if cfg.AllowCredentials && cfg.AllowOrigins == "*" {
    panic("INSECURE CORS: Cannot use wildcard origin with credentials")
}

✅ RECOMMENDED SECURE CONFIGURATION

// SECURE - Specific origins with credentials
app.Use(cors.New(cors.Config{
    AllowOrigins: "https://yourdomain.com,https://app.yourdomain.com",
    AllowCredentials: true,
}))

// SECURE - Wildcard without credentials
app.Use(cors.New(cors.Config{
    AllowOrigins: "*",
    AllowCredentials: false,
}))

📚 REFERENCES & RESOURCES

Thanks for reading!

Disclaimer: This material is for informational purposes only, and should not be construed as legal advice or opinion. For actual legal advice, you should consult with professional legal services.

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