Overview
The CVE-2026-33531 advisory describes a path traversal vulnerability in InvenTree's Python-based template engine, where a staff-level user who can upload or edit templates could craft template tags that read arbitrary files from the server filesystem. This class of vulnerability arises when a template engine evaluates user-modifiable templates and exposes functions that access the filesystem, allowing an attacker to traverse paths and fetch sensitive files outside the application directory. While this CVE targets a Python project, the underlying risk is template injection combined with unsafe file-access, demonstrated by file reads via crafted template content. The impact can be severe, including exposure of configuration, credentials, and project data, and is mitigated by ensuring templates are not user-controlled and by removing or safely restricting any file-system access from template functions. The report explicitly references CVE-2026-33531 (CWE-89: Improper Neutralization of Special Elements used in an SQL Command, extended here to template injection risk) and notes that patched versions exist (1.2.6 and 1.3.0+ for InvenTree). In Go (Gin) contexts, this vulnerability manifests as template injection risks when user-controlled templates or unsafe template functions can read arbitrary server files. To prevent this, Go apps should avoid evaluating untrusted templates, or constrain templates to a fixed, non-user-modifiable set, and remove any file-access operations from template-supplied code paths. Implementing a strict allowlist of templates and precompiling them removes the attack surface while preserving the intended rendering behavior.
Affected Versions
Prior to 1.2.6; patched in 1.2.6 and 1.3.0+ for the InvenTree project (CVE-2026-33531)
Code Fix Example
Go (Gin) API Security Remediation
VULNERABLE PATTERN (Go Gin, risky):
package main
import (
"bytes"
"net/http"
"os"
"text/template"
"github.com/gin-gonic/gin"
)
func main() {
r := gin.Default()
// Dangerous: user-supplied template is parsed with a function that can read files
r.GET("/render", func(c *gin.Context) {
tmpl := c.Query("tmpl") // attacker-controlled content
t, err := template.New("tmpl").Funcs(template.FuncMap{
"readFile": func(path string) string {
b, _ := os.ReadFile(path)
return string(b)
},
}).Parse(tmpl)
if err != nil {
c.String(http.StatusBadRequest, "template parse error")
return
}
var out bytes.Buffer
if err := t.Execute(&out, map[string]string{"Name": "World"}); err != nil {
c.String(http.StatusInternalServerError, "render error")
return
}
c.String(http.StatusOK, out.String())
})
r.Run()
}
FIXED PATTERN (Go Gin):
package main
import (
"bytes"
"log"
"net/http"
"github.com/gin-gonic/gin"
"text/template"
)
func main() {
// Precompile allowed templates (no user-supplied template parsing)
templates := map[string]*template.Template{
"hello": template.Must(template.New("hello").Parse("Hello, {{.Name}}!")),
}
r := gin.Default()
r.GET("/render", func(c *gin.Context) {
tmplName := c.Query("tmpl")
t, ok := templates[tmplName]
if !ok {
c.String(http.StatusBadRequest, "unknown template")
return
}
var buf bytes.Buffer
if err := t.Execute(&buf, map[string]string{"Name": "World"}); err != nil {
c.String(http.StatusInternalServerError, "render error")
return
}
c.String(http.StatusOK, buf.String())
})
if err := r.Run(); err != nil {
log.Fatal(err)
}
}