@rhinostone/swig: arbitrary local file read via include/extends path traversal

Overview

@rhinostone/swig is a maintained fork of the abandoned swig template engine and inherited the directory-traversal vulnerability tracked upstream as CVE-2023-25345 / GHSA-2rq5-699j-x7p6. The {% include %}, {% extends %}, and {% import %} tags resolve their target path through the filesystem loader without confining the result to the configured template root. A path that traverses upward (../) escapes the root and reads an arbitrary file from the host filesystem, whose contents are emitted into the rendered output.

Attack scenario

The dangerous case does not require the attacker to control template source — only template data (the locals passed at render time). An application that renders a trusted template whose include / extends path is variable-driven is exposed:

// application code — a configured filesystem loader with a basepath
swig.renderFile('page.html', { partial: req.query.partial });

{# page.html — trusted template #}
{% include partial %}

Setting ?partial=../../../../etc/passwd makes the loader resolve and read that file, and its contents are rendered into the response. A literal in trusted source is equally affected: {% include "../../../etc/passwd" %}.

Impact

Arbitrary local file disclosure (confidentiality). An attacker able to influence an include / extends / import path — directly, or via untrusted locals — can read files outside the template directory: application configuration, credentials, source code, /etc/passwd, and so on. There is no integrity or availability impact.

Affected & patched

Every published version up to and including 2.7.0 is affected — @rhinostone/swig, and the shared @rhinostone/swig-core loader, hence @rhinostone/swig-twig, @rhinostone/swig-jinja2, and @rhinostone/swig-django as well.

Fixed in 2.7.1: the filesystem loader now rejects any / / path that resolves outside the configured root, including paths supplied through an untrusted runtime variable. A new loader option is available for the rare case of intentionally reading files from outside the root.