Executive brief
Tugtainer, a tool used to automate Docker container updates, contains a security flaw in its notification system. An attacker with a valid login can use this flaw to take complete control of the application and execute commands as a root user. This could lead to the theft of sensitive data, access to other containers on the same server, or a total shutdown of the service.
Technical details
Tugtainer versions prior to 1.30.2 are vulnerable to Server-Side Template Injection (SSTI) within the notification template feature. The root cause is the use of an unsandboxed `jinja2.Environment` in `backend/core/notifications_core.py` to render the `title_template` and `body_template` fields. An authenticated attacker can submit malicious Jinja2 expressions via the `/api/settings/test_notification` endpoint to escape the template environment and access Python built-ins. This allows for Remote Code Execution (RCE) as the root user within the container. Because the application often has access to the Docker socket, an attacker could potentially compromise the entire host or other containers. The issue is resolved in version 1.30.2 by migrating to `jinja2.sandbox.SandboxedEnvironment`.
Affected products
- Quenary Tugtainer < 1.30.2
Timeline
- 2026-05-20: advisory: Original GitHub security advisory published
- 2026-07-23: disclosed: CVE published to NVD
- 2026-07-23: patched: Version 1.30.2 released to address the vulnerability