Overview
This vulnerability (CVE-2026-33432) shows how an unauthenticated attacker can bypass authentication by manipulating LDAP search filters through unsafely concatenated user input. In Roxy-WI, LDAP authentication concatenated the supplied login name directly into the LDAP filter, enabling injection of metacharacters that altered the query to return a different user entry or bypass checks entirely. The impact is severe: attacker can gain access without a valid password, escalating to unauthorized control of the web interface that manages HAProxy, Nginx, Apache, and Keepalived. The CVE notes that versions up to and including 8.2.8.2 are affected, with no patches available at the time of publication. This guide uses that CVE as a concrete example of how Broken Authentication can arise from improper LDAP filter construction in Go-based services using Gin, and provides Go code patterns to avoid such flaws in authentication flows.
In Go (Gin) applications, the vulnerability manifests when building LDAP query filters by interpolating user-supplied values without escaping special LDAP characters. Attackers can inject characters like *, (, ), and | into the username field to alter the filter logic, potentially matching unintended entries or bypassing password checks. Mitigation requires escaping all user input before inserting into LDAP filters, or better, using LDAP libraries’ escaping utilities or safe query composition patterns. This aligns with the CWE-287 category (Improper Authentication) and demonstrates the real-world risk of trusting user input in authentication logic in Go services.
The remediation focus for Go (Gin) projects is to reject patterns that rely on direct string concatenation for LDAP filters, replace them with escapes, and adopt secure authentication flow practices. Key steps include escaping username values with ldap.EscapeFilter (or equivalent), binding with a service account for directory searches, and verifying credentials by attempting a user bind with the provided password. Additionally, enforce transport security (LDAPS, StartTLS), limit login attempts, audit authentication failures, and add automated tests that simulate LDAP injection attempts. Implementing these changes reduces the risk of Broken Authentication via LDAP filter injection in Gin-based backends and aligns with the CVE-2026-33432 findings.
Affected Versions
Roxy-WI <= 8.2.8.2
Code Fix Example
Go (Gin) API Security Remediation
// -- Vulnerable (concatenation) vs. Fixed (escape) in one file --
package main
import (
"fmt"
"log"
"net/http"
"github.com/gin-gonic/gin"
ldap "github.com/go-ldap/ldap/v3"
)
type LoginRequest struct {
Username string `json:"username"`
Password string `json:"password"`
}
func main(){
r := gin.Default()
r.POST("/login/vulnerable", loginVulnerable)
r.POST("/login/fixed", loginFixed)
log.Fatal(r.Run(":8080"))
}
func ldapConnect() (*ldap.Conn, error) {
l, err := ldap.Dial("tcp", "ldap.example.com:389")
if err != nil {
return nil, err
}
// In production, enable StartTLS or LDAPS
return l, nil
}
func loginVulnerable(c *gin.Context) {
var req LoginRequest
if err := c.ShouldBindJSON(&req); err != nil {
c.JSON(http.StatusBadRequest, gin.H{"error": "invalid"})
return
}
l, err := ldapConnect()
if err != nil {
c.JSON(http.StatusInternalServerError, gin.H{"error": "ldap connect"})
return
}
defer l.Close()
// Vulnerable: directly injects user input into LDAP filter
filter := fmt.Sprintf("(&(objectClass=person)(sAMAccountName=%s))", req.Username)
searchRequest := ldap.NewSearchRequest("dc=example,dc=com", ldap.ScopeWholeSubtree, ldap.NeverDerefAliases, 0, 0, false, filter, []string{"dn"}, nil)
sr, err := l.Search(searchRequest)
if err != nil {
c.JSON(http.StatusUnauthorized, gin.H{"error": "invalid credentials"})
return
}
if len(sr.Entries) == 0 {
c.JSON(http.StatusUnauthorized, gin.H{"error": "invalid credentials"})
return
}
c.JSON(http.StatusOK, gin.H{"status": "authenticated (vulnerable path)"})
}
func loginFixed(c *gin.Context){
var req LoginRequest
if err := c.ShouldBindJSON(&req); err != nil {
c.JSON(http.StatusBadRequest, gin.H{"error": "invalid"})
return
}
l, err := ldapConnect()
if err != nil {
c.JSON(http.StatusInternalServerError, gin.H{"error": "ldap connect"})
return
}
defer l.Close()
// Fixed: escape user input before constructing LDAP filter
safe := ldap.EscapeFilter(req.Username)
filter := fmt.Sprintf("(&(objectClass=person)(sAMAccountName=%s))", safe)
searchRequest := ldap.NewSearchRequest("dc=example,dc=com", ldap.ScopeWholeSubtree, ldap.NeverDerefAliases, 0, 0, false, filter, []string{"dn"}, nil)
sr, err := l.Search(searchRequest)
if err != nil {
c.JSON(http.StatusUnauthorized, gin.H{"error": "invalid credentials"})
return
}
if len(sr.Entries) == 0 {
c.JSON(http.StatusUnauthorized, gin.H{"error": "invalid credentials"})
return
}
c.JSON(http.StatusOK, gin.H{"status": "authenticated (fixed path)"})
}