The security bug discovered in the Linux kernel's implementation of the TCP protocol also affects a large portion of the Android ecosystem, mobile security vendor Lookout reports.
According to researchers, CVE-2016-5696, the Linux TCP bug, affects around 80 percent of all Android devices in use today, which is around 1.4 billion devices. The reason for this is the fact that the Android OS is built on a modified version of the Linux kernel.
The Linux Foundation has already taken all the steps to mitigate this security flaw, having patched the Linux kernel on July 11, 2016.
The security bug, CVE-2016-5696, allows an attacker who is not in a man-in-the-middle position to probe servers or users for active connections and then guess the packet sequence.
This enables the attacker to enter the packet flow between two parties, sniff on unencrypted traffic, or shut down encrypted connections. All Linux kernel versions between v3.6 and up to v4.7 are vulnerable.
The first vulnerable version that featured this TCP implementation flaw, version 3.6, was released in 2012 and was also used to create the Android OS 4.4 (KitKat).
Since security researchers disclosed the flaw last week, Google has not yet released any security patches. Google usually releases security patches at the start of each month, but it is highly unlikely that the Android OS would feature a security patch for such a massive feature like the TCP stack just after a few weeks.
Even if security vendors have not discovered any weaponized exploit utilizing this flaw, Lookout recommends that all users protect themselves by encrypting their traffic.
Users can do this by using encrypted apps, navigating sites via their HTTPS versions, or by employing a VPN. For more technical users, the Lookout team recommends the following steps:
If you have a rooted Android device you can make this attack harder by using the sysctl tool and changing the value for net.ipv4.tcp_challenge_ack_limit to something very large, e.g. net.ipv4.tcp_challenge_ack_limit = 999999999