CVE-2026-42545: Granian vulnerable to DoS via WSGI response header panic

Granian aborts a worker process if a WSGI application returns an invalid HTTP response header name or value. The WSGI response conversion path uses .unwrap() on both the header name and header value constructors, so malformed output from the application becomes a process abort instead of a handled error.

This issue requires a buggy or attacker-influenced WSGI application to emit invalid headers. It is not a parser bug in Granian’s request path. The security impact is that application mistakes which should result in a 500 instead kill the worker process.