Copier's safe template hat beliebigen Dateisystem-Lese-/Schreibzugriff

The vulnerability stems from insufficient security measures within Copier's Jinja templating system. While Copier attempts to restrict file access through the {% include ... %} directive, limitations in Jinja extensions and custom configurations can be exploited. An attacker could craft a malicious template that bypasses these restrictions, enabling them to read arbitrary files from the system. The potential data at risk includes configuration files, source code, and any other sensitive information accessible through the filesystem. Lateral movement is unlikely directly from this vulnerability, but successful file access could reveal credentials or other information that facilitates further attacks.

Organizations and developers using Copier for project generation, particularly those relying on custom Jinja extensions or templates from untrusted sources, are at risk. Shared hosting environments where multiple users utilize Copier could also be vulnerable if templates are not properly isolated.

• python / project-generator:

import os
import subprocess

def check_copier_version():
    try:
        result = subprocess.run(['copier', '--version'], capture_output=True, text=True, check=True)
        version = result.stdout.strip()
        if version <= '9.9.0':
            print(f"Copier version is vulnerable: {version}")
        else:
            print(f"Copier version is patched: {version}")
    except FileNotFoundError:
        print("Copier is not installed.")
    except subprocess.CalledProcessError as e:
        print(f"Error checking Copier version: {e}")

check_copier_version()

• generic web: Check Copier configuration files for references to custom Jinja extensions or potentially unsafe template features.

1. 2025-08-18Disclosure

   disclosure

1. Reserviert2025-08-08
2. Veröffentlicht2025-08-18
3. EPSS aktualisiert2026-03-23

The primary mitigation is to upgrade Copier to version 9.9.1 or later, which addresses the vulnerability by strengthening Jinja template security. If an immediate upgrade is not feasible, consider implementing stricter controls on template sources. Carefully review and validate all templates used by Copier, ensuring they do not utilize potentially unsafe Jinja extensions or custom configurations. Implement a Web Application Firewall (WAF) with rules to detect and block requests containing malicious Jinja code. Monitor Copier logs for unusual file access patterns or attempts to execute unauthorized commands. After upgrade, confirm by attempting to access a restricted file via a crafted template and verifying access is denied.