Researchers discovered that a Transmission Control Protocol (TCP) specification implemented in Linux creates a vulnerability that can be exploited to terminate connections and conduct data injection attacks.
The flaw, tracked as CVE-2016-5696, is related to a feature described in RFC 5961, which should make it more difficult to launch off-path TCP spoofing attacks. The specification was formulated in 2010, but it has not been fully implemented in Windows, Mac OS X, and FreeBSD-based operating systems. However, the feature has been implemented in the Linux kernel since version 3.6, released in 2012.
A team of researchers from the University of California, Riverside and the U.S. Army Research Laboratory identified an attack method that allows a blind, off-path attacker to intercept TCP-based connections between two hosts on the Internet.
Researchers noted that data cannot be injected into HTTPS communications, but the connection can still be terminated using this method. One attack scenario described by the experts involves targeting Tor by disrupting connections between certain relays so that users are forced to use attacker-controlled exit relays.