Memory Leak in Linux Kernel Bluetooth HCI Connection

Executive Summary

This vulnerability is a memory leak in the Linux kernel's Bluetooth subsystem, specifically in the function hci_le_big_terminate().

The issue occurs when the function allocates memory for iso_list_data using kzalloc_obj but fails to free it in a specific error path. If neither the pa_sync_term nor big_sync_term flags are set after evaluating the PA and BIG sync connection state, the function returns 0 without freeing the allocated memory.

This early-return path was introduced during a refactor of hci_le_big_terminate(), where the function was modified to accept a struct hci_conn instead of raw u8 parameters, adding logic to evaluate PA/BIG flags. The existing kfree() call only handles failures in hci_cmd_sync_queue and does not cover this specific path.

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Detection Guidance

Detecting this specific vulnerability (CVE-2026-53364) on your network or system is challenging because it is a memory leak in the Linux kernel's Bluetooth subsystem, which does not manifest obvious external symptoms. However, you can check for the following indicators:

• Verify the Linux kernel version: This vulnerability affects the Linux kernel. Check your kernel version using the command 'uname -r'. If the kernel version is vulnerable, you may need to update it.
• Monitor Bluetooth subsystem logs: Use 'dmesg | grep Bluetooth' or check system logs ('journalctl -u bluetooth') for any unusual errors or warnings related to Bluetooth connections, particularly involving PA/BIG sync termination.
• Check for memory leaks: Use tools like 'kmemleak' (if enabled in your kernel) or 'slabtop' to monitor kernel memory usage. Look for unexpected memory growth in Bluetooth-related allocations.

Note that these methods are indirect and may not definitively confirm the presence of this specific vulnerability. The most reliable detection method is to verify if your kernel version is affected and apply the necessary patches.

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Impact Analysis

This vulnerability can impact you in the following ways:

• Memory exhaustion: The memory leak can accumulate over time, leading to increased memory usage by the kernel. This may degrade system performance or cause the system to run out of memory, potentially resulting in crashes or instability.
• Denial of Service (DoS): An attacker could exploit this vulnerability to repeatedly trigger the memory leak, causing the system to become unresponsive or crash. This could disrupt services or applications relying on the affected system.
• Limited scope: The impact is confined to systems using Bluetooth with the affected Linux kernel versions. The vulnerability does not allow for arbitrary code execution or privilege escalation, so the risk of direct data compromise is low.

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Compliance Impact

This vulnerability may have implications for compliance with certain standards and regulations, depending on the context in which the affected system is used:

• GDPR (General Data Protection Regulation): If the affected system processes personal data of EU citizens and the memory leak leads to system instability or crashes, it could result in a loss of availability of personal data. GDPR requires that personal data be processed securely, including ensuring availability. A prolonged outage due to this vulnerability could be seen as a failure to meet these requirements.
• HIPAA (Health Insurance Portability and Accountability Act): For systems handling protected health information (PHI) in the U.S., this vulnerability could pose a risk if it leads to system downtime or instability. HIPAA requires that PHI be available and protected against threats to its integrity and availability. If the memory leak causes disruptions in accessing PHI, it could be considered a compliance violation.
• General security standards (e.g., ISO 27001, NIST): Many security frameworks require organizations to manage vulnerabilities and ensure system stability. This vulnerability, if left unpatched, could be flagged during audits as a failure to maintain secure systems, potentially leading to non-compliance.

However, the direct impact on compliance depends on whether the affected system is part of a regulated environment and how severely the vulnerability disrupts operations or data availability.

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Mitigation Strategies

To mitigate this vulnerability (CVE-2026-53364), follow these steps:

• Update the Linux kernel: Apply the latest kernel updates from your distribution vendor. This vulnerability has been resolved in the upstream Linux kernel, so updating to a patched version is the most effective mitigation.
• Disable Bluetooth if not in use: If Bluetooth functionality is not required, disable it to eliminate the attack surface. This can be done by stopping the Bluetooth service ('systemctl stop bluetooth') or blacklisting the Bluetooth kernel modules.
• Monitor for patches: If an immediate kernel update is not feasible, monitor for backported patches from your distribution and apply them as soon as they become available.
• Limit Bluetooth exposure: Restrict Bluetooth access to trusted devices only and avoid using Bluetooth in untrusted environments to reduce the risk of exploitation.

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