Where on IIS can the HTTP_HOST environment variable be overridden?

Question

IIS

Please tell me:
I inherited a project on ASP.NET MVC, I'm poking around in the settings. Request.ServerVariables["HTTP_HOST"] returns an invalid domain name. I began to pick IIS settings, Google points to the UrlRewrite module setting, but I either don’t have it installed, or it’s called differently, it’s very likely that in IIS 8 it was renamed to “Handler Mapping”.
But I didn't find any traces there either. Where else can an incorrect value come from?