Sitecore is setting same language cookie multiple times in response headers

Question

Our multi-site Sitecore instance (7.0.- rev-130424) is setting same language cookie multiple times like below in response headers:

Set-Cookie: SiteName#lang=de-DE; path=/; secure; HttpOnly 
Set-Cookie:  SiteName#lang=de-DE; path=/; secure; HttpOnly 
Set-Cookie:  SiteName#lang=de-DE; path=/; secure; HttpOnly

This is happening like 40-50 odd times in some pages, because of the exceeded header counts, load balancers are not processing those pages. Have any of you faced this issue before?

Answer 1

I know this answer is late but just answering in case it might help someone else. I believe this is an ASP .NET bug more details can be found in this SO answer. Putting below code in the EndRequest event fixed this for me:

try
{
    var guid = Guid.NewGuid();
    HttpContext.Current.Response.Cookies.Add(new HttpCookie(guid.ToString(), string.Empty));
    HttpContext.Current.Response.Cookies.Remove(guid.ToString());
}
catch (HttpException)
{
    //This means the headers were already written,
    //in which case we need not do anything.
}