Bluetooth L2CAP Slab-Use-After-Free Vulnerability in Linux Package
Summary
DEBIAN-CVE-2025-21969: In the Linux kernel, the following vulnerability has been resolved: Bluetooth: L2CAP: Fix slab-use-after-free Read in l2cap_send_cmd After the hci sync command releases l2cap_conn, the hci receive data work queue referen... Affects linux versions < 6.12.20-1. Fixed in 6.12.20-1. How to fix ↓
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Background
The Linux package is a core component of the Debian operating system, responsible for managing hardware and system resources. It provides essential functionalities such as process management, memory management, and device control. This package is critical for system stability and performance, making it a prime target for vulnerabilities that could compromise system integrity.
Vulnerability Detail
The vulnerability identified as DEBIAN-CVE-2025-21969 is a slab-use-after-free issue in the Bluetooth L2CAP subsystem of the Linux kernel. This flaw occurs when the hci sync command releases the l2cap_conn structure, but the hci receive data work queue still references this released structure when sending data to the upper layer. This can lead to potential memory corruption and system instability, allowing an attacker to exploit the flaw to execute arbitrary code or crash the system.
How To Fix
Minimum fixed version
6.12.20-1
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 workaround, users can disable Bluetooth functionality if it is not required for their operations. This can be done by executing the command:
sudo systemctl stop bluetooth' to stop the Bluetooth service until the package is updated.
Conclusion
The Bluetooth L2CAP slab-use-after-free vulnerability in the Linux package poses significant risks to system integrity and security. Users are strongly advised to update their systems to the latest patched version to mitigate these risks. Temporary workarounds, such as disabling Bluetooth, can provide additional protection until updates are applied.
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FAQ
A slab-use-after-free vulnerability occurs when a program continues to use a memory area after it has been freed, potentially leading to memory corruption and exploitation.
You can use Vulert to monitor and alert for open-source vulnerabilities in your software. Visit Vulert Scanner to check if your application is affected without requiring any signup.
Exploitation of this vulnerability could allow an attacker to execute arbitrary code, leading to system crashes or unauthorized access to sensitive information.
Yes, the permanent fix is to update the Linux package to version 6.12.20-1 or later, which addresses the vulnerability.
If immediate updates are not possible, consider disabling Bluetooth functionality as a temporary measure to reduce exposure to the vulnerability.
References
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