CVE-2024-26890 is a medium severity vulnerability in the Linux kernel's Bluetooth subsystem, specifically within the btrtl driver which handles Realtek Bluetooth chipsets. The issue arises due to an out-of-bounds memory access detected by the Kernel Address Sanitizer (KASAN). The root cause is improper memory allocation for private HCI (Host Controller Interface) data when the btrtl driver is used in conjunction with the hci_h5 transport layer. While the btusb transport correctly allocates memory for the private data structure 'struct btrealtek_data', the hci_h5 transport does not allocate this memory, leading to an out-of-bounds write during initialization. This flaw can cause a slab-out-of-bounds write, potentially leading to kernel memory corruption, instability, or crashes. The vulnerability was identified through a detailed kernel stack trace involving Bluetooth driver functions such as hci_dev_open_sync and hci_power_on. The affected Linux kernel versions include those around the commit hash 5b355944b19011011dd3fd4187444c5ff1d76ad2. The CVSS 3.1 score is 6.5 (medium), reflecting that the vulnerability can be exploited remotely without privileges or user interaction, impacting availability and confidentiality to a limited extent. No known exploits are reported in the wild yet. The underlying weakness corresponds to CWE-125 (Out-of-bounds Read). This vulnerability is significant because Bluetooth is widely used for device connectivity, and kernel-level bugs can compromise system stability and security. The fix involves proper memory allocation for the private HCI data when using the hci_h5 transport, preventing the out-of-bounds access.

For European organizations, this vulnerability poses a moderate risk primarily to systems running Linux kernels with affected versions and utilizing Bluetooth with Realtek chipsets via the btrtl driver and hci_h5 transport. Potential impacts include system crashes or denial of service due to kernel memory corruption, which can disrupt business operations, especially in environments relying on Bluetooth for critical device communication (e.g., IoT devices, industrial control systems, or mobile devices). Confidentiality impact is limited but possible if memory corruption leads to information leakage. Since exploitation does not require privileges or user interaction and can be triggered remotely via Bluetooth, attackers within wireless range could potentially exploit this flaw to destabilize systems or cause service interruptions. This is particularly relevant for organizations with mobile workforces, public-facing Linux servers with Bluetooth enabled, or embedded Linux devices in operational technology. However, the absence of known exploits reduces immediate risk, though proactive patching is advised to prevent future exploitation.

1. Apply the official Linux kernel patches that address CVE-2024-26890 as soon as they become available from trusted sources or Linux distribution vendors. 2. For systems where immediate patching is not feasible, consider disabling Bluetooth functionality temporarily, especially on devices using Realtek chipsets with the btrtl driver and hci_h5 transport. 3. Implement strict Bluetooth device pairing policies and limit Bluetooth usage to trusted devices only, reducing exposure to potential attackers within wireless range. 4. Monitor kernel logs for KASAN reports or unusual Bluetooth driver errors that may indicate attempted exploitation or instability. 5. For embedded or IoT devices, coordinate with vendors to ensure firmware updates include this fix. 6. Employ network segmentation and endpoint security controls to limit the impact of compromised devices. 7. Educate users and administrators about the risks of Bluetooth vulnerabilities and encourage disabling Bluetooth when not in use.