vLLM: DoS via unbounded chat_template Jinja2 rendering exhausts the renderer thread pool

Summary vLLM renders chat templates by passing the resolved Jinja2 source to tokenizer.applychattemplate, which compiles and .renders it in an ImmutableSandboxedEnvironment. The sandbox prevents code-execution escapes but imposes no wall-clock timeout, no output-size cap, and no nested-loop or...