Tugtainer, a self‑hosted tool for automating Docker container updates, contains a Server‑Side Template Injection flaw in its notification template feature. The title_template and body_template fields are rendered with an unsandboxed jinja2.Environment, which allows any authenticated user to inject Jinja2 expressions that are executed as root inside the container. Versions prior to 1.30.2 are vulnerable, and the issue is fixed in release 1.30.2. Because the application runs with root privileges within the container, such injections give full control of that environment, and the vulnerability is classified as CWE‑1336. Based on the description, it is inferred that an authenticated user must access the notification template interface to inject malicious code.

This issue affects all Quenary tugtainer installations running any version earlier than 1.30.2. The vendor advisory lists version 1.30.2 as the first release that incorporates the fix.

The CVSS score of 9.9 signifies an extremely high severity and the EPSS score of less than 1% suggests that the probability of exploitation in the wild is currently low, although the impact is catastrophic. The flaw is not in the CISA KEV catalog, which implies no confirmed exploits have been reported yet. Based on the description, the attacker must first authenticate to the application and then create or modify a notification template with malicious Jinja2 code. Once executed, the attacker gains root control within the container, providing severe impact to all data and operations within that container.