Broken Function Level Authorization

Broken Function Level Authorization in Go (Gin) [Sep 2025] [CVE-2025-10731]

[Updated Sep 2025] Updated CVE-2025-10731

Overview

CVE-2025-10731 describes a sensitive information exposure in a WordPress plugin where unauthenticated attackers can obtain authentication tokens and bypass admin restrictions to export sensitive data. While this CVE targets a WordPress product, it illustrates the same class of risk: function-level authorization can be broken when a service only enforces access at a high level or inside a single function. In Go with Gin, a similar issue appears when endpoints are guarded only by a global auth check, and the specific function that accesses a resource performs no explicit or sufficient authorization checks. In a Go (Gin) API, an attacker could call a route that accepts a resource identifier (for example, an order or user record) and retrieve information without verifying the caller's permissions. The fix is to enforce authorization at the resource boundary: verify ownership or require an admin role before returning sensitive data, ideally via middleware or per-handler checks that are explicit and testable. Remediation steps for Go (Gin) include: add per-endpoint RBAC or ownership checks; validate the authenticated user against the resource owner; apply explicit admin-only guards on privileged endpoints; centralize authorization logic in middleware or helper functions; test with unit and integration tests to prevent BFLA regressions.

Code Fix Example

Go (Gin) API Security Remediation
package main\n\nimport (\n  \"github.com/gin-gonic/gin\"\n  \"net/http\"\n)\n\ntype User struct {\n  ID string\n  Role string\n}\n\ntype Order struct {\n  ID string\n  OwnerID string\n  Data string\n}\n\nvar users = map[string]User{\n  \"u1\": {ID: \"u1\", Role: \"user\"},\n  \"admin\": {ID: \"admin\", Role: \"admin\"},\n}\n\nvar orders = []Order{\n  {ID: \"o1\", OwnerID: \"u1\", Data: \"secret-order-odata\"},\n}\n\nfunc mockAuthMiddleware() gin.HandlerFunc {\n  return func(c *gin.Context) {\n    userID := c.GetHeader(\"X-User\")\n    if user, ok := users[userID]; ok {\n      c.Set(\"user\", user)\n    }\n    c.Next()\n  }\n}\n\nfunc currentUser(c *gin.Context) (User, bool) {\n  v, ok := c.Get(\"user\")\n  if !ok {\n    return User{}, false\n  }\n  u, _ := v.(User)\n  return u, true\n}\n\nfunc vulnerableHandler(c *gin.Context) {\n  orderID := c.Param(\"orderID\")\n  for _, o := range orders {\n    if o.ID == orderID {\n      c.JSON(http.StatusOK, o)\n      return\n    }\n  }\n  c.Status(http.StatusNotFound)\n}\n\nfunc fixedHandler(c *gin.Context) {\n  orderID := c.Param(\"orderID\")\n  user, ok := currentUser(c)\n  if !ok {\n    c.Status(http.StatusUnauthorized)\n    return\n  }\n  for _, o := range orders {\n    if o.ID == orderID {\n      if user.Role != \"admin\" && o.OwnerID != user.ID {\n        c.Status(http.StatusForbidden)\n        return\n      }\n      c.JSON(http.StatusOK, o)\n      return\n    }\n  }\n  c.Status(http.StatusNotFound)\n}\n\nfunc main() {\n  r := gin.Default()\n  r.Use(mockAuthMiddleware())\n\n  r.GET(\"/vuln/orders/:orderID\", vulnerableHandler)\n  r.GET(\"/secure/orders/:orderID\", fixedHandler)\n\n  r.Run(\":8080\")\n}\n

CVE References

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