Overview
CVE-2026-7305 describes a server-side request forgery (SSRF) risk in a Java project (Xxl-job) where the triggerJob flow manipulated an addressList to cause remote requests, potentially exploited remotely. The CVE references CWE-918 and notes that the exploit publicized could be mitigated by login/access controls, though real-world existence is debated by maintainers. This guide references that CVE specifically to illustrate the same SSRF risk class in Go with Gin: when a handler uses user-controlled input to perform a server-side request, an attacker can cause the application to fetch internal or restricted resources. In Go (Gin), this typically happens when a query parameter or payload is passed directly to http.Get or an HTTP client, enabling requests to internal services, metadata endpoints, or other sensitive hosts. The material here maps the generic SSRF class from the CVE into concrete Go/Gin remediation patterns, with a concrete, working code example that demonstrates both the vulnerable and fixed approaches. The focus is on preventing unauthenticated or unaudited remote fetches via user input, and on implementing robust validation, host allowlisting, and network protections to mitigate similar threats in Go services.
Code Fix Example
Go (Gin) API Security Remediation
package main
import (
"fmt"
"io/ioutil"
"net"
"net/http"
"net/url"
"time"
"github.com/gin-gonic/gin"
)
// Vulnerable and fixed endpoints are served from the same file for side-by-side comparison.
// Vulnerable: directly fetches a URL supplied by the user (SSRF risk)
func vulnerableFetchHandler(c *gin.Context) {
raw := c.Query("url")
resp, err := http.Get(raw)
if err != nil {
c.String(http.StatusBadRequest, err.Error())
return
}
defer resp.Body.Close()
body, _ := ioutil.ReadAll(resp.Body)
c.Data(resp.StatusCode, resp.Header.Get("Content-Type"), body)
}
// Simple private IP check helper
func isPrivateIP(ip net.IP) bool {
if ip4 := ip.To4(); ip4 != nil {
switch {
case ip4[0] == 10:
return true
case ip4[0] == 172 && ip4[1] >= 16 && ip4[1] <= 31:
return true
case ip4[0] == 192 && ip4[1] == 168:
return true
case ip4[0] == 127:
return true
}
}
return false
}
// Allowed hosts for fixed version
var allowedHosts = map[string]struct{}{
"example.com": {},
"cdn.example.com": {},
}
// Fixed: validates and restricts the target URL before fetching
var httpClient = &http.Client{
Timeout: 5 * time.Second,
Transport: &http.Transport{
Proxy: http.ProxyFromEnvironment,
},
}
func isAllowedURL(u *url.URL) bool {
if u.Scheme != "http" && u.Scheme != "https" {
return false
}
host := u.Hostname()
if _, ok := allowedHosts[host]; !ok {
return false
}
ips, err := net.LookupIP(host)
if err != nil {
return false
}
for _, ip := range ips {
if ip.IsLoopback() || isPrivateIP(ip) {
return false
}
}
return true
}
func fetchSafe(target string) ([]byte, error) {
u, err := url.Parse(target)
if err != nil {
return nil, err
}
if !isAllowedURL(u) {
return nil, fmt.Errorf("host not allowed")
}
resp, err := httpClient.Get(u.String())
if err != nil {
return nil, err
}
defer resp.Body.Close()
return ioutil.ReadAll(resp.Body)
}
func fixedFetchHandler(c *gin.Context) {
raw := c.Query("url")
data, err := fetchSafe(raw)
if err != nil {
c.String(http.StatusBadRequest, "invalid url: %v", err)
return
}
c.Data(http.StatusOK, "application/octet-stream", data)
}
func main() {
r := gin.Default()
r.GET("/vuln/fetch", vulnerableFetchHandler)
r.GET("/fix/fetch", fixedFetchHandler)
_ = r.Run(":8080")
}