CVE-2024-35856 is a vulnerability identified in the Linux kernel's Bluetooth USB Mediatek driver (btusb). The flaw arises from improper memory management in the function hci_devcd_append(), which handles Bluetooth communication data structures. Specifically, the function frees a socket buffer (skb) on error conditions, but the caller also attempts to free the same skb, leading to a double free scenario. A double free vulnerability occurs when the same memory is deallocated twice, which can corrupt the kernel's memory management structures. This corruption can potentially be exploited by an attacker to cause a denial of service (system crash) or, in more severe cases, to execute arbitrary code with kernel privileges. The vulnerability affects certain versions of the Linux kernel that include the Mediatek Bluetooth USB driver implementation. The issue was reported by Dan Carpenter and has been addressed by correcting the memory management logic to ensure skb is freed only once. No known exploits are currently reported in the wild, and no CVSS score has been assigned yet. However, the vulnerability resides in a critical kernel component responsible for Bluetooth communication, which is widely used in many Linux distributions and devices.

For European organizations, this vulnerability poses a risk primarily to systems running Linux kernels with the affected Mediatek Bluetooth USB driver. Many enterprises, government agencies, and critical infrastructure operators in Europe rely on Linux-based systems for servers, desktops, and embedded devices. Exploitation could lead to system instability or crashes, impacting availability of services. In worst-case scenarios, attackers could leverage this flaw to escalate privileges and gain control over affected systems, threatening confidentiality and integrity of sensitive data. The impact is heightened in environments where Bluetooth connectivity is essential, such as IoT deployments, industrial control systems, or mobile computing devices. Although no active exploits are known, the presence of this vulnerability in the kernel means that attackers with local access or Bluetooth interface access could attempt to trigger the flaw. Given the widespread use of Linux in European IT infrastructure, the potential impact includes disruption of business operations, data breaches, and increased risk to critical systems.

European organizations should prioritize patching Linux kernel versions that include the Mediatek Bluetooth USB driver as soon as vendor updates become available. Since the vulnerability involves kernel-level memory management, updating to the fixed kernel release is the most effective mitigation. In the interim, organizations can reduce risk by disabling Bluetooth functionality on systems where it is not required, especially on servers and critical infrastructure devices. Network segmentation and strict access controls should be enforced to limit local access to vulnerable systems. Monitoring system logs for unusual Bluetooth activity or kernel errors can help detect attempts to exploit the flaw. Additionally, organizations should ensure that endpoint security solutions are up to date and capable of detecting anomalous behavior related to kernel memory corruption. For embedded or IoT devices using affected Linux kernels, coordination with device vendors for firmware updates is essential. Finally, applying a comprehensive vulnerability management process to track and remediate this and related kernel vulnerabilities will reduce exposure.