CVE-2026-74529 in Linux
Summary
by MITRE • 08/15/2026
In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: hci_sync: hold conn in hci_connect_pa_sync() callback
There is theoretical UAF if the conn is freed while the hci_sync task is running.
Hold refcount to avoid that.
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Analysis
by VulDB Data Team • 08/15/2026
The vulnerability in question involves a potential use-after-free condition within the Linux kernel's Bluetooth subsystem, specifically affecting the HCI (Host Controller Interface) synchronization mechanism. This issue manifests in the hci_sync task where a connection object may be freed while still being referenced by an ongoing asynchronous operation, creating a scenario that could potentially be exploited by malicious actors.
The technical flaw occurs within the hci_connect_pa_sync() callback function where the system fails to maintain proper reference counting for connection objects. When the hci_sync task executes asynchronously, it operates on connection data structures that might be prematurely deallocated by other kernel components or concurrent operations. This creates a race condition where the memory previously occupied by a freed connection object could be reallocated and accessed by the hci_sync task, resulting in undefined behavior and potential security implications.
According to CWE classification, this vulnerability maps to CWE-416 Use After Free, which describes a situation where code continues to reference memory after it has been freed by its original owner. The operational impact of such a vulnerability extends beyond simple system instability, as it could potentially allow privilege escalation or denial-of-service conditions within the kernel space. The theoretical nature of this UAF suggests that while the vulnerability may not be easily exploitable in all scenarios, it represents a significant security risk given the kernel's privileged execution context.
The mitigation strategy requires implementing proper reference counting mechanisms to ensure that connection objects remain valid for the duration of the hci_sync task execution. This approach aligns with standard kernel security practices and follows the principle of maintaining object lifetime guarantees in concurrent environments. The fix involves explicitly incrementing and decrementing reference counts to prevent premature deallocation during asynchronous operations.
This vulnerability demonstrates the complexity of kernel-level synchronization issues where multiple execution paths must coordinate safely without creating race conditions or memory access violations. It reflects common challenges in embedded systems programming where real-time constraints and asynchronous processing intersect with memory management principles. The ATT&CK framework would categorize this under privilege escalation techniques through kernel vulnerabilities, as exploitation could potentially allow attackers to gain elevated privileges within the system.
The resolution addresses fundamental security principles around resource management and synchronization in kernel space operations. Proper reference counting ensures that objects remain accessible for all parties that might be using them concurrently, preventing scenarios where freed memory is accessed by asynchronous tasks. This fix exemplifies defensive programming practices essential for maintaining kernel stability and security across various Bluetooth implementations and device configurations.
Modern Linux kernel development increasingly emphasizes such safety mechanisms to prevent subtle but dangerous race conditions in complex subsystems like Bluetooth HCI drivers. The vulnerability highlights the ongoing need for rigorous testing of concurrent code paths and proper memory management practices in kernel modules where timing-sensitive operations interact with dynamic resource allocation.