Overview
SQL injection vulnerabilities in login flows can enable attackers to bypass authentication, access or modify user data, and potentially take over accounts. While CVE-2026-29861 describes PHP-MYSQL-User-Login-System v1.0, the underlying risk-unsafely interpolated input in a login query-is a class of vulnerability that can affect any tech stack, including Go with Gin, if user input is concatenated into SQL strings.
The CVE-2026-29861 entry states that a SQL injection flaw existed via the username parameter at login.php, illustrating how an attacker can craft input to alter the query logic. This demonstrates why dynamic query construction without parameterization is dangerous and can lead to authentication bypass and data exposure.
In Go (Gin) apps, this risk manifests when developers build SQL statements by string concatenation or fmt.Sprintf with request parameters (e.g., username) and execute them directly. If the username or password comes from req.Query or req.Form, an attacker can inject SQL that always returns true, or leak data.
Remediate by using parameterized queries and prepared statements through database/sql, validating inputs, using password hashing, and applying least-privilege DB accounts. This guide shows how to fix the pattern in Go code, with a vulnerable and a fixed version side by side, and steps to apply in your project.
Code Fix Example
Go (Gin) API Security Remediation
package main
import (
"database/sql"
"fmt"
"log"
"github.com/gin-gonic/gin"
_ "github.com/go-sql-driver/mysql"
)
var db *sql.DB
func main() {
var err error
db, err = sql.Open("mysql", "user:password@tcp(127.0.0.1:3306)/dbname")
if err != nil {
log.Fatal(err)
}
defer db.Close()
r := gin.Default()
r.GET("/vulnerable/login", vulnerableLogin)
r.GET("/secure/login", secureLogin)
r.Run(":8080")
}
func vulnerableLogin(c *gin.Context) {
username := c.Query("username")
password := c.Query("password")
// Vulnerable: string concatenation leads to SQL injection
query := fmt.Sprintf("SELECT EXISTS(SELECT 1 FROM users WHERE username='%s' AND password='%s')", username, password)
var exists bool
err := db.QueryRow(query).Scan(&exists)
if err != nil {
c.JSON(500, gin.H{"error": "internal error"})
return
}
if exists {
c.JSON(200, gin.H{"status": "logged_in"})
} else {
c.JSON(401, gin.H{"status": "unauthorized"})
}
}
func secureLogin(c *gin.Context) {
username := c.Query("username")
password := c.Query("password")
// Secure: parameterized query
query := "SELECT EXISTS(SELECT 1 FROM users WHERE username=? AND password=?)"
var exists bool
err := db.QueryRow(query, username, password).Scan(&exists)
if err != nil {
c.JSON(500, gin.H{"error": "internal error"})
return
}
if exists {
c.JSON(200, gin.H{"status": "logged_in"})
} else {
c.JSON(401, gin.H{"status": "unauthorized"})
}
}