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The vulnerability exists because the Gin web framework’s default configuration implicitly trusts all proxy headers. When an application is initiated using gin.Default(), the `TrustedProxies` field is set to a wildcard value (0.0.0.0/0). This setting instructs the framework to accept the `X-Forwarded-For` and `X-Real-IP` headers from any incoming connection as the authoritative source for the client’s IP address when `ClientIP()` is called. Consequently, IP-based security mechanisms such as IP whitelists, `AllowIPs` middleware, and localhost-only checks that depend on `ClientIP()` for validation are fundamentally compromised. A remote attacker can simply forge an HTTP request containing a header like X-Forwarded-For: 127.0.0.1. The application, trusting this spoofed header, will compute the client’s IP as 127.0.0.1, thereby granting the attacker unauthorized access that was intended to be restricted to the local machine or a specific set of trusted IP addresses.
DailyCVE Form:
Platform: Gin Web Framework
Version: < v1.6.0
Vulnerability: Proxy Header Spoofing
Severity: Critical
Date: 2020-01-01
Prediction: Patch: 2020-02-15
What Undercode Say:
Analytics:
grep -r "ClientIP()" core/middleware/ grep -r "gin.Default()" --include=".go" cat go.mod | grep gin
// Vulnerable initialization
router := gin.Default()
// Secure initialization
router := gin.New()
router.SetTrustedProxies([]string{"192.168.1.0/24"})
How Exploit:
curl -H "X-Forwarded-For: 127.0.0.1" http://target/api/restricted
Protection from this CVE:
Explicitly configure `TrustedProxies` using `SetTrustedProxies()` with specific CIDR ranges of your legitimate reverse proxies. Avoid using `gin.Default()` in production; use `gin.New()` instead and configure middleware manually.
Impact:
Complete bypass of IP-based access controls, allowing remote attackers to impersonate whitelisted IPs including localhost.
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Sources:
Reported By: github.com
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