GHSA-wgh7-7m3c-fx25: Scriban has Uncontrolled Recursion in Parser Leads to Stack Overflow and Process Crash (Denial of Service)

Scriban is vulnerable to an uncontrolled process crash resulting in a Denial of Service. Because the recursive-descent parser does not enforce a default limit on expression depth, an attacker who controls template input can craft a heavily nested template that triggers a StackOverflowException. In .NET, a StackOverflowException cannot be caught by standard try-catch blocks, resulting in the immediate and ungraceful termination of the entire hosting process.

Scriban utilizes a recursive-descent parser to process template expressions. While the library exposes an ExpressionDepthLimit property in its ParserOptions, this property defaults to null (disabled).

If an application accepts user-supplied templates (or dynamically constructs templates from untrusted input), an attacker can supply thousands of nested parentheses or blocks. As the parser recursively evaluates each nested layer, it consumes thread stack space until it exceeds the limits of the host OS, triggering a fatal crash.