A non‑internal redirect is triggered when the `uenc` query parameter is supplied to the `stockAction()` method in OpenMage's Magento LTS. If the provided `product_id` does not match a catalog product, the server redirects the client to the URL supplied in `uenc` via an HTTP 302 response without validating that the target URL is internal. This flaw is a classic open‑redirect vulnerability (CWE‑601) that can be abused to trick users into visiting malicious sites or to facilitate phishing attacks.

The vulnerability affects all installations of OpenMage Magento LTS running a version earlier than 20.18.0. No additional sub‑version details are specified, so any instance below 20.18.0 is considered susceptible.

With a CVSS score of 6.1 the flaw is rated moderate severity. The EPSS score is not reported and the issue is not listed in the CISA KEV catalog, indicating no known large‑scale exploitation to date. Remote attackers can trigger the redirect by crafting a URL containing the `uenc` parameter, so the attack vector is network‑based, requiring only standard HTTP access to the exposed endpoint.