Compliance Impact

This vulnerability allows arbitrary file read by bypassing the configured root directory restriction, enabling attackers to access files outside the intended sandbox.

Such unauthorized access to local files could lead to exposure of sensitive or personal data, which may violate data protection regulations like GDPR or HIPAA if the compromised files contain protected information.

Therefore, applications using vulnerable versions of liquidjs that rely on the root option as a sandbox boundary and pass attacker-controlled template names to renderFile() or parseFile() risk non-compliance with these standards due to potential data breaches.

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Executive Summary

CVE-2026-39859 is a vulnerability in the liquidjs npm package (versions up to and including 10.25.4) that allows an attacker to read arbitrary files on the server. This happens because the top-level file loading functions renderFile() and parseFile() do not properly enforce the configured root directory restriction, allowing files outside the intended sandbox to be accessed.

Although liquidjs documents that the root option should constrain filenames, the enforcement is missing for top-level file loads. This means that even if a Liquid instance is configured with a safe temporary directory as root, an attacker can bypass this and read sensitive files like /etc/hosts by passing absolute paths to these functions.

The root cause is that the code disables the enforceRoot flag for top-level file lookups, accepting resolved paths without verifying if they reside within the root directory. This contrasts with stricter checks applied to partial, layout, and include lookups.

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Impact Analysis

This vulnerability can lead to unauthorized disclosure of sensitive local files on the server where liquidjs is used. An attacker who can control template names passed to renderFile() or parseFile() can read arbitrary files outside the intended sandbox.

Such file disclosure can expose configuration files, credentials, or other sensitive data, potentially leading to further attacks or data breaches.

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Detection Guidance

This vulnerability can be detected by testing whether the LiquidJS instance allows reading files outside the configured root directory using the renderFile() or parseFile() functions.

A practical detection method is to attempt rendering a file outside the root directory, such as /etc/hosts, and observe if the contents are returned.

For example, if you have access to the application code or a testing environment, you can run a script that calls renderFile('/etc/hosts') on a Liquid instance configured with a safe temporary directory as root. If the file contents are returned, the vulnerability is present.

There are no specific network commands provided in the resources, but monitoring for unexpected file read operations or unusual template rendering requests that include absolute paths could help detect exploitation attempts.

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Mitigation Strategies

The immediate mitigation step is to upgrade liquidjs to version 10.25.3 or later, where the vulnerability is fixed by enforcing containment checks on top-level file loads.

If upgrading is not immediately possible, avoid configuring Liquid instances with an empty or unsafe root directory and do not pass untrusted or attacker-controlled template names to renderFile() or parseFile().

Additionally, review your application code to ensure that the root directory option is properly set and that template file paths are validated to prevent path traversal.

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