Overview
The CVE-2026-33301 vulnerability in OpenEMR demonstrates how unescaped or improperly validated input can flow into a document generation path, enabling an attacker to influence generated content by including arbitrary server resources (such as images) in a PDF. In OpenEMR prior to version 8.0.0.2, users with the Notes - my encounters role could fill Eye Exam forms and print a PDF where the form answers were parsed as HTML without proper escaping, allowing an attacker to cause arbitrary file reads by embedding server-side images into the PDF. This type of injection arises when untrusted input is consumed by a downstream renderer without strict context-appropriate encoding. The issue, categorized under CWE-116 (Improper Encoding or Escaping of Output), was fixed in OpenEMR 8.0.0.2 and highlights how untrusted data can contaminate content generation pipelines and leak or manipulate server content.
In Go with Gin, similar injection vulnerabilities occur when user input is mishandled and flows into contexts like SQL, HTML rendering, or shell interactions. If input is concatenated into SQL statements, the app becomes vulnerable to SQL injection; if user-supplied data is embedded directly into HTML without escaping, client-side scripts can execute (XSS) or content can be manipulated. The OpenEMR CVE underscores the risk of taking untrusted data and feeding it into downstream rendering or file-generation steps without proper validation and escaping. In Go, the canonical defenses are to use parameterized queries for all database access and to render HTML via the html/template package (which escapes output by default) rather than concatenating strings or bypassing escaping when composing documents or responses.
This guide shows concrete Go (Gin) patterns: a vulnerable handler that constructs SQL with string concatenation and a vulnerable HTML assembly path, and their fixed counterparts that use parameterized queries and proper HTML escaping via html/template. Treat these as concrete, real-world remediation patterns you can apply to similar injection points in your Go services.
Affected Versions
OpenEMR 8.0.0.0 - 8.0.0.1 (prior to 8.0.0.2)
Code Fix Example
Go (Gin) API Security Remediation
package main
import (
"bytes"
"database/sql"
"html/template"
"log"
"net/http"
"github.com/gin-gonic/gin"
_ "github.com/mattn/go-sqlite3"
)
func main() {
db := setupDB()
defer db.Close()
r := gin.Default()
// Vulnerable pattern: SQL concatenation and raw HTML assembly
r.GET("/vuln/sql", func(c *gin.Context) {
id := c.Query("id")
row := db.QueryRow("SELECT name FROM users WHERE id = " + id) // vulnerability
var name string
if err := row.Scan(&name); err != nil {
c.String(http.StatusBadRequest, "invalid id")
return
}
c.String(http.StatusOK, "User: "+name)
})
// Fixed pattern: parameterized SQL query
r.GET("/fix/sql", func(c *gin.Context) {
id := c.Query("id")
var name string
if err := db.QueryRow("SELECT name FROM users WHERE id = ?", id).Scan(&name); err != nil {
c.String(http.StatusBadRequest, "invalid id")
return
}
c.String(http.StatusOK, "User: "+name)
})
// Vulnerable: unsafely concatenated HTML (XSS)
r.GET("/vuln/template", func(c *gin.Context) {
note := c.Query("note")
html := "<html><body>" + note + "</body></html>"
c.Data(http.StatusOK, "text/html; charset=utf-8", []byte(html))
})
// Fixed: use html/template to escape content
r.GET("/fix/template", func(c *gin.Context) {
note := c.Query("note")
t := template.Must(template.New("report").Parse("<html><body>{{.Note}}</body></html>"))
var buf bytes.Buffer
if err := t.Execute(&buf, map[string]string{"Note": note}); err != nil {
c.String(http.StatusInternalServerError, "render error")
return
}
c.Data(http.StatusOK, "text/html; charset=utf-8", buf.Bytes())
})
r.Run(":8080")
}
func setupDB() *sql.DB {
db, err := sql.Open("sqlite3", ":memory:")
if err != nil { log.Fatal(err) }
if _, err := db.Exec("CREATE TABLE users (id INTEGER PRIMARY KEY, name TEXT)"); err != nil { log.Fatal(err) }
if _, err := db.Exec("INSERT INTO users (name) VALUES ('Alice'), ('Bob')"); err != nil { log.Fatal(err) }
return db
}