Last Updated: 2011-12-28 23:02:14 UTC
by Daniel Wesemann (Version: 2)
A new vulnerability advisory by security firm n-runs  describes how hash tables in PHP5,Java,ASP.NET and others can be attacked with deliberate collisions in the hash function, leading to a denial of service (DoS) on the web server in question. Microsoft have already responded with an advisory  of their own, other vendors are likely to follow.
Updated 2300UTC: MSFT published additional information  on how to detect and mitigate an attack.