Use-After-Free Vulnerability in Linux Kernel Bluetooth Module
Summary
CVE-2021-33034: In the Linux kernel before 5.12.4, net/bluetooth/hci_event.c has a use-after-free when destroying an hci_chan, aka CID-5c4c8c954409. Affects linux versions < 5.10.38-1. Fixed in 5.10.38-1. How to fix ↓
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Background
The Linux kernel is a core component of many operating systems, providing essential services for hardware and software interaction. It supports a wide range of functionalities, including networking, file systems, and device management. The Bluetooth module within the kernel facilitates wireless communication between devices. However, prior to version 5.12.4, a critical vulnerability was identified in the Bluetooth handling code, specifically in the hci_event.c file, which could lead to severe security risks.
Vulnerability Detail
In the Linux kernel versions before 5.12.4, a use-after-free vulnerability exists in the Bluetooth subsystem, particularly when destroying an hci_chan. This flaw allows an attacker to write arbitrary values to memory locations, potentially leading to system crashes, unauthorized access, or execution of malicious code. The vulnerability is classified under CVE-2021-33034 and has a CVSS score of 7.8, indicating a high severity level.
How To Fix
Minimum fixed version
5.10.38-1
This is the first release that contains the fix.
sudo apt-get install --only-upgrade linuxTip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
As a temporary measure, users can disable Bluetooth functionality until the kernel is updated. This can be done by executing the following command in the terminal:
sudo systemctl stop bluetooth.service
Conclusion
The CVE-2021-33034 vulnerability in the Linux kernel Bluetooth module poses significant security risks due to a use-after-free flaw. Users are advised to update their systems promptly to mitigate potential threats. Utilizing tools like Vulert can help in monitoring for such vulnerabilities effectively.
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FAQ
A use-after-free vulnerability occurs when a program continues to use a memory reference after it has been freed, potentially allowing an attacker to manipulate the memory.
You can use the Vulert platform to monitor and alert for open-source vulnerabilities. Simply upload your manifest file like package-lock.json to check for vulnerabilities.
Exploitation of this vulnerability can lead to arbitrary code execution, system crashes, or unauthorized access to sensitive data.
Disabling Bluetooth functionality is a temporary workaround, but it is strongly recommended to update the kernel as soon as possible.
Detailed information can be found in the CVE database or through security advisories related to the Linux kernel.
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