A vulnerability in the Quarkus Qute template engine leads to improper output escaping when using the {#eval} section helper. When EvalSectionHelper parses a sub-template, it fails to pass the parent template's Variant (which dictates the content type, such as HTML or JSON). Because Qute's standard escapers (HtmlEscaper, JsonEscaper) require this variant to determine if and how escaping should be applied, they silently bypass the evaluated content. As a result, any untrusted data processed inside an {#eval} block is output as raw, unescaped text.

A flaw was found in the Qute template engine, which is used by Quarkus to generate dynamic content like HTML pages or emails. The issue exists in the component responsible for looking up data values (ReflectionValueResolver), which fails to properly block access to sensitive Java internal functions when processing certain data types like Enums. An attacker who can provide or influence the template text can exploit this bypass to take control of the server by executing unauthorized commands.