Assume that you try to sign in to a Windows Server 2012 R2-based Security Token Service (STS) server in a passive way through an STS Proxy. When the sign-in request includes more than 20 cookies, the sign-in fails.
This issue occurs because a STS proxy is limited to transfer no more than 20 cookies to the STS server, and the additional cookies are dropped on the corresponding back-end STS request by the STS proxy.
To resolve this issue, install update rollup 2962409. For more information about how to obtain this update rollup package, click the following article number to view the article in the Microsoft Knowledge Base:
2962409 Windows RT 8.1, Windows 8.1, and Windows Server 2012 R2 update rollup: June 2014
To work around this issue, you must clear all the browser cookies under the Delete Browsing History under Internet Options in Internet Explorer.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base:
824684 Description of the standard terminology that is used to describe Microsoft software updates