Winter CMS versions before 1.2.13 contain an incomplete patch that leaves a Twig sandbox escape flaw in System\\Twig\\SecurityPolicy. The flaw allows authenticated backend users who have permission to edit templates to bypass the sandbox rules that normally prevent arbitrary PHP execution. Attackers can forward calls through Eloquent models and query builders to invoke methods such as saveQuietly(), deleteQuietly(), increment(), decrement(), and newQuery(), enabling them to read and alter any database table, execute arbitrary SQL statements, and inject PHP code into the template rendering process. This results in loss of confidentiality, integrity, and availability of the application as attackers gain remote code execution capabilities.

All Winter CMS installations that are running any release older than 1.2.13 are susceptible. The affected vendor product is Winter CMS by wintercms. No patch version is listed in the input, but updates beyond 1.2.13 resolve the issue.

The vulnerability carries a CVSS score of 9.3, indicating a critical severity. Although the EPSS score is not provided, the lack of a public exploit and the requirement for authenticated template‑editing privileges suggest a moderate to high likelihood of exploitation in environments where backend access is not tightly controlled. The vulnerability is not listed in the CISA KEV catalog, yet the potential for remote code execution makes it a priority for immediate remediation.