Google Warns of Zero-Click Bluetooth Flaws in Linux-based Devices

Google security researchers are warning of a new set of zero-click vulnerabilities in the Linux Bluetooth software stack that can allow a nearby unauthenticated, remote attacker to execute arbitrary code with kernel privileges on vulnerable devices.

According to security engineer Andy Nguyen, the three flaws — collectively called BleedingTooth — reside in the open-source BlueZ protocol stack that offers support for many of the core Bluetooth layers and protocols for Linux-based systems such as laptops and IoT devices.

The first and the most severe is a heap-based type confusion (CVE-2020-12351, CVSS score 8.3) affecting Linux kernel 4.8 and higher and is present in the Logical Link Control and Adaptation Protocol (L2CAP) of the Bluetooth standard, which provides multiplexing of data between different higher layer protocols.

“A remote attacker in short distance knowing the victim’s [Bluetooth device] address can send a malicious l2cap packet and cause denial of service or possibly arbitrary code execution with kernel privileges,” Google noted in its advisory. “Malicious Bluetooth chips can trigger the vulnerability as well.”

The vulnerability, which is yet to be addressed, appears to have been introduced in a change to the “l2cap_core.c” module made in 2016.

Intel, which has significantly invested in the BlueZ project, has also issued an alert characterizing CVE-2020-12351 as a privilege escalation flaw.

The second unpatched vulnerability (CVE-2020-12352) concerns a stack-based information disclosure flaw affecting Linux kernel 3.6 and higher.

A consequence of a 2012 change made to the core Alternate MAC-PHY Manager Protocol (A2MP) — a high-speed transport link used in Bluetooth HS (High Speed) to enable the transfer of larger amounts of data — the issue permits a remote attacker in short distance to retrieve kernel stack information, using it to predict the memory layout and defeat address space layout randomization (KASLR)

Lastly, a third flaw (CVE-2020-24490) discovered in HCI (Host Controller Interface), a standardized Bluetooth interface used for sending commands, receiving events, and for transmitting data, is a heap-based buffer overflow impacting Linux kernel 4.19 and higher, causing a nearby remote attacker to “cause denial of service or possibly arbitrary code execution with kernel privileges on victim machines if they are equipped with Bluetooth 5 chips and are in scanning mode.”

The vulnerability, which has been accessible since 2018, has been patched in versions 4.19.137 and 5.7.13.

For its part, Intel has recommended installing the kernel fixes to mitigate the risk associated with these issues.

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

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