Interview: James Kettle Explains HTTP Desync Attacks (In Under 3 Minutes)

$70k - how's that for a bug bounty total netted from an almost forgotten web exploit?

At Black Hat USA 2019 in Las Vegas, James Kettle of Portswigger Web Security demonstrated how he pulled it off. The security researcher used an old (by internet standards) technique called HTTP Request Smuggling, which was first documented back in 2005.

It still works. Kettle's exploit schemes, dubbed Desync Attacks, leverage the HTTP protocol support for sending multiple HTTP  requests over a single underlying TCP or SSL/TLS socket.

HTTP requests are traditionally understood as isolated entities that are placed back to back. In his presentation of request smuggling attacks for cybersecurity researchers, Kettle showed how he was able to overcome this compartmentalization.

The British threat hunter's approach enabled him to splice requests into others, as he said, to "gain maximum privilege  access to internal APIs, poison web caches, and compromise what's possibly your most trusted login page."

How did he do it? And what does it mean for a web browser accessing an impacted web server?  Amir Mohammadi asked him for episode # 18 of The Silo Sessions podcast:

Listen to their conversation here.