CVE-2026-24425: Twig: Possible sandbox bypass when using a source policy

When using the sandbox with a SourcePolicyInterface, Twig does not always apply the sandbox restriction that forbids non-Closure callbacks for callback-accepting filters.

The issue affects the sort, filter, map, and reduce filters.

In the affected versions, the runtime check that rejects non-Closure callbacks in sandbox mode does not use the current template Source. As a result, when the sandbox is enabled through a source policy instead of being enabled globally, Twig can incorrectly treat the current execution as non-sandboxed for these callback checks.

This can allow user-controlled templates to pass arbitrary PHP callables to callback-accepting filters even though the template is being sandboxed through a source policy.

The issue happens when all these conditions are met:

• The sandbox is not enabled globally;
• A SourcePolicyInterface enables the sandbox for the rendered template;
• The template uses one of the sort, filter, map, or reduce filters;
• The callback is not a Closure.