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GHSA-RJR7-JGGH-PGCP

Vulnerability from github – Published: 2026-06-25 18:19 – Updated: 2026-06-25 18:19
VLAI
Summary
chi's RealIP Middleware allows IP spoofing via unvalidated X-Forwarded-For header
Details

Summary

realip middleware in go-chi/chi trusts headers like x-forwarded-for without checking them, so attackers can fake their ip and bypass rate limits or access controls

Details

the vuln is in middleware/realip.go , the realIP() function pulls IPs straight from client headers and replaces r.RemoteAddr without checking if the request came from a trusted proxy

func realIP(r *http.Request) string {
    var ip string
    if tcip := r.Header.Get(trueClientIP); tcip != "" {
        ip = tcip  // controlled by attacker
    } else if xrip := r.Header.Get(xRealIP); xrip != "" {
        ip = xrip  // controlled by attacker
    } else if xff := r.Header.Get(xForwardedFor); xff != "" {
        ip, _, _ = strings.Cut(xff, ",")  // controlled by attacker
    }
    // ...
    return ip
}

no trusted proxy cidr check in place, any client can send these headers

PoC

create a server with chi and use realip middleware

package main

import (
    "fmt"
    "net/http"
    "github.com/go-chi/chi/v5"
    "github.com/go-chi/chi/v5/middleware"
)

func main() {
    r := chi.NewRouter()
    r.Use(middleware.RealIP)

    r.Get("/admin", func(w http.ResponseWriter, r *http.Request) {
        // ip-based access control got bypassed
        if r.RemoteAddr == "127.0.0.1" {
            w.Write([]byte("SECRET ADMIN DATA"))
            return
        }
        http.Error(w, "Forbidden", 403)
    })

    http.ListenAndServe(":8080", r)
}

spoofed the ip to bypass access control

curl -H "X-Forwarded-For: 127.0.0.1" http://localhost:8080/admin

Impact

  • ip-based access control bypass lets attackers reach restricted endpoints
  • rate limiting bypass lets attackers avoid limits by rotating spoofed ips
  • audit logs show fake ips picked by attacker instead of real ones
  • attackers can get around geo ip restrictions

Remediation Recommendation

validate proxy cidr first before trusting forwarded ip headers

// add your reverse proxy ip addresses here
var trustedProxies = []net.IPNet{
       {IP: net.ParseIP("10.0.0.0"), Mask: net.CIDRMask(8, 32)},
    {IP: net.ParseIP("172.16.0.0"), Mask: net.CIDRMask(12, 32)},
    {IP: net.ParseIP("192.168.0.0"), Mask: net.CIDRMask(16, 32)},
}

func isTrustedProxy(ip net.IP) bool {
    for _, cidr := range trustedProxies {
        if cidr.Contains(ip) {
            return true
        }
    }
    return false
}
Severity
7.7 (High)
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:P
Show details on source website
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/go-chi/chi/middleware"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "last_affected": "1.5.5"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/go-chi/chi/v2/middleware"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "last_affected": "2.1.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/go-chi/chi/v3/middleware"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "last_affected": "3.3.5"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/go-chi/chi/v4/middleware"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "last_affected": "4.1.3"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/go-chi/chi/v5/middleware"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "5.3.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [],
  "database_specific": {
    "cwe_ids": [
      "CWE-290",
      "CWE-348"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-06-25T18:19:15Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "details": "### Summary\nrealip middleware in go-chi/chi trusts headers like x-forwarded-for without checking them, so attackers can fake their ip and bypass rate limits or access controls\n\n### Details\n\nthe vuln is in middleware/realip.go , the realIP() function pulls IPs straight from client headers and replaces r.RemoteAddr without checking if the request came from a trusted proxy\n\n```go\nfunc realIP(r *http.Request) string {\n    var ip string\n    if tcip := r.Header.Get(trueClientIP); tcip != \"\" {\n        ip = tcip  // controlled by attacker\n    } else if xrip := r.Header.Get(xRealIP); xrip != \"\" {\n        ip = xrip  // controlled by attacker\n    } else if xff := r.Header.Get(xForwardedFor); xff != \"\" {\n        ip, _, _ = strings.Cut(xff, \",\")  // controlled by attacker\n    }\n    // ...\n    return ip\n}\n```\n\nno trusted proxy cidr check in place, any client can send these headers\n\n### PoC\n\ncreate a server with chi and use realip middleware\n\n```go\npackage main\n\nimport (\n    \"fmt\"\n    \"net/http\"\n    \"github.com/go-chi/chi/v5\"\n    \"github.com/go-chi/chi/v5/middleware\"\n)\n\nfunc main() {\n    r := chi.NewRouter()\n    r.Use(middleware.RealIP)\n\n    r.Get(\"/admin\", func(w http.ResponseWriter, r *http.Request) {\n        // ip-based access control got bypassed\n        if r.RemoteAddr == \"127.0.0.1\" {\n            w.Write([]byte(\"SECRET ADMIN DATA\"))\n            return\n        }\n        http.Error(w, \"Forbidden\", 403)\n    })\n\n    http.ListenAndServe(\":8080\", r)\n}\n```\n\nspoofed the ip to bypass access control\n\n```bash\ncurl -H \"X-Forwarded-For: 127.0.0.1\" http://localhost:8080/admin\n```\n\n\n### Impact\n\n- ip-based access control bypass lets attackers reach restricted endpoints\n- rate limiting bypass lets attackers avoid limits by rotating spoofed ips\n- audit logs show fake ips picked by attacker instead of real ones\n- attackers can get around geo ip restrictions\n\n## Remediation Recommendation\n\nvalidate proxy cidr first before trusting forwarded ip headers\n\n```go\n// add your reverse proxy ip addresses here\nvar trustedProxies = []net.IPNet{\n       {IP: net.ParseIP(\"10.0.0.0\"), Mask: net.CIDRMask(8, 32)},\n    {IP: net.ParseIP(\"172.16.0.0\"), Mask: net.CIDRMask(12, 32)},\n    {IP: net.ParseIP(\"192.168.0.0\"), Mask: net.CIDRMask(16, 32)},\n}\n\nfunc isTrustedProxy(ip net.IP) bool {\n    for _, cidr := range trustedProxies {\n        if cidr.Contains(ip) {\n            return true\n        }\n    }\n    return false\n}\n```",
  "id": "GHSA-rjr7-jggh-pgcp",
  "modified": "2026-06-25T18:19:15Z",
  "published": "2026-06-25T18:19:15Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/go-chi/chi/security/advisories/GHSA-rjr7-jggh-pgcp"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/go-chi/chi"
    },
    {
      "type": "WEB",
      "url": "https://github.com/go-chi/chi/releases/tag/v5.3.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:P",
      "type": "CVSS_V4"
    }
  ],
  "summary": "chi\u0027s RealIP Middleware allows IP spoofing via unvalidated X-Forwarded-For header"
}



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