Google and Intel warn of high-severity Bluetooth security bug in Linux

By | October 14, 2020
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Google and Intel are warning of a high-severity Bluetooth flaw in all but the most recent version of the Linux Kernel. While a Google researcher said the bug allows seamless code execution by attackers within Bluetooth range, Intel is characterizing the flaw as providing an escalation of privileges or the disclosure of information.

The flaw resides in BlueZ, the software stack that by default implements all Bluetooth core protocols and layers for Linux. Besides Linux laptops, it’s used in many consumer or industrial Internet-of-things devices. It works with Linux versions 2.4.6 and later.

In search of details

So far, little is known about BleedingTooth, the name given by Google engineer Andy Nguyen, who said that a blog post will be published “soon.” A Twitter thread and a YouTube video provide the most detail and give the impression that the bug provides a reliable way for nearby attackers to execute malicious code of their choice on vulnerable Linux devices that use BlueZ for Bluetooth.

“BleedingTooth is a set of zero-click vulnerabilities in the Linux Bluetooth subsystem that can allow an unauthenticated remote attacker in short distance to execute arbitrary code with kernel privileges on vulnerable devices,” the researcher wrote. He said his discovery was inspired by research that led to BlueBorne, another proof-of-concept exploit that allowed attackers to send commands of their choice without requiring device users click any links, connect to a rogue Bluetooth device, or take any other action short of having Bluetooth turned on.

Below is the YouTube video demonstrating how the exploit works.

BleedingTooth: Linux Bluetooth Zero-Click Remote Code Execution

Intel, meanwhile, has issued this bare-bones advisory that categorizes the flaw as privilege-escalation or information-disclosure vulnerability. The advisory assigned a severity score of 8.3 out of a possible 10 to CVE-2020-12351, one of three distinct bugs that comprise BleedingTooth.

“Potential security vulnerabilities in BlueZ may allow escalation of privilege or information disclosure,” the advisory states. “BlueZ is releasing Linux kernel fixes to address these potential vulnerabilities.”

Intel, which is a primary contributor to the BlueZ open source project, said that the most effective way to patch the vulnerabilities is to update to Linux kernel version 5.9, which was published on Sunday. Those who can’t upgrade to version 5.9 can install a series of kernel patches the advisory links to. Maintainers of BlueZ didn’t immediately respond to emails asking for additional details about this vulnerability.

No reason to (kernel) panic

The lack of details aside, there’s not much reason for people to worry about a vulnerability like this one. Like almost all Bluetooth security flaws, BleedingTooth requires proximity to a vulnerable device. It also requires highly specialized knowledge and works on only a tiny fraction of the world’s Bluetooth devices. Those limitations greatly reduce the number of people—if any—who are in a position to successfully carry out an attack.

In the small number of cases where financially motivated attackers do target wireless devices within range—for instance, when credit card fraudsters used telescopic antennas outside a Marshalls store to hack retailer TJX more than a decade ago—they don’t use experimental, state-of-the-art exploits that work on a narrow range of devices. They use tried-and-true hacks that work universally.

“I don’t really worry about bugs like these,” Dan Guido, mobile security specialist and the CEO of security firm Trail of Bits, told me. “I’m glad someone is finding them and getting them fixed, but it’s not a big concern for me.”

The lack of real-world risk is a good thing. Many IoT devices receive few if any security updates, making it likely that many devices used in both homes and businesses will remain vulnerable to BleedingTooth for the rest of the time they’re used. Many of these devices were likely already vulnerable to BlueBorne and several other security bugs that have bitten Bluetooth in the past. So far, there are no reports of any of them being actively exploited.