SECURITY UPDATE: heap buffer overflow via post-rewrite URI to path
mapping with alias
debian/patches/CVE-2026-15176.patch: in ngx_http_map_uri_to_path(),
reject the mapping for a location using "alias" when r->uri_changed is
set, so a rewritten URI shorter than the location prefix is no longer
mapped to a path (e.g. via $request_filename)
debian/patches/CVE-2026-15176-2.patch: in ngx_http_script_break_code(),
clear r->valid_location when the URI was changed, so the alias check
also rejects the mapping after a standalone "break"