drivers/net/wireless/realtek/rtlwifi/ps.c in the Linux kernel through
5.3.6 lacks a certain upper-bound check, leading to a buffer overflow.
A potentially serious vulnerability in Linux may make it possible for
nearby devices to use Wi-Fi signals to crash or fully compromise
vulnerable machines, a security researcher said.
The flaw is located in the RTLWIFI driver, which is used to support
Realtek Wi-Fi chips in Linux devices. The vulnerability triggers a buffer overflow
in the Linux kernel when a machine with a Realtek Wi-Fi chip is within
radio range of a malicious device. At a minimum, exploits would cause an
operating-system crash and could possibly allow a hacker to gain
complete control of the computer. The flaw dates back to version 3.10.1
of the Linux kernel released in 2013.
“The bug is serious,” Nico Waisman, who is a principal security
engineer at Github, told Ars. “It’s a vulnerability that triggers an
overflow remotely through Wi-Fi on the Linux kernel, as long as you’re
using the Realtek (RTLWIFI) driver.”
The vulnerability is tracked as CVE-2019-17666. Linux developers proposed a fix
on Wednesday that will likely be incorporated into the OS kernel in the
coming days or weeks. Only after that will the fix make its way into
various Linux distributions.
Waisman said he has not yet devised a proof-of-concept attack that
exploits the vulnerability in a way that can execute malicious code on a
“I’m still working on exploitation, and it will definitely… take
some time (of course, it might not be possible),” he wrote in a direct
message. “On paper, [this] is an overflow that should be exploitable.
Worst-case scenario, [this] is a denial of service; best scenario, you
get a shell.”
After the vulnerability became public, the researcher discussed the flaw on Twitter.
Notice of Absence
The driver flaw can be triggered when an affected device is within
radio range of a malicious device. As long as the Wi-Fi is turned on, it
requires no interaction on the part of the end user. The malicious
device exploits the vulnerability by using a power-saving feature known
as a Notice of Absence that’s built into Wi-Fi Direct,
a standard that allows two devices to connect over Wi-Fi without the
need of an access point. The attack would work by adding vendor-specific
information elements to Wi-Fi beacons that, when received by a
vulnerable device, trigger the buffer overflow in the Linux kernel.
The vulnerability only affects Linux devices that use a Realtek chip
when Wi-Fi is turned on. The flaw can’t be triggered if Wi-Fi is turned
off or if the device uses a Wi-Fi chip from a different manufacturer.
Based on links here and here, it appears that Android devices with Realtek Wi-Fi chips may also be affected.
Representatives of both Realtek and Google didn’t immediately comment on this story.
While it’s still not clear how severely this vulnerability can be
exploited, the prospect of code-execution attacks that can be staged
wirelessly by devices within radio range is serious. This post will be
updated if new information becomes available.
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