CVE-2026-68391 in Linux
Summary
by MITRE • 08/10/2026
In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: mgmt: hold reference for hci_conn in mgmt_pending_cmds
Dereferencing RCU-protected pointers outside critical sections is invalid and may lead to UAF. Use of hci_conn in hci_sync callbacks also needs to hold refcount to avoid UAF.
Take appropriate locks for hci_conn lookups, and take refcount for hci_conn pointers stored in mgmt_pending_cmd so that the pointer stays valid.
When accessing conn->state, ensure hdev->lock is held to avoid data race.
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Analysis
by VulDB Data Team • 08/10/2026
This vulnerability resides within the Linux kernel's Bluetooth subsystem, specifically addressing improper reference counting and synchronization mechanisms in the management interface code. The issue stems from inadequate handling of hci_conn references during Bluetooth connection management operations, creating potential for use-after-free conditions that could be exploited by malicious actors. The flaw manifests when RCU-protected pointers are accessed outside their designated critical sections, violating fundamental memory safety principles that govern concurrent access patterns in kernel space.
The technical implementation involves the mgmt_pending_cmds structure which maintains references to hci_conn objects without proper reference counting mechanisms. When hci_sync callbacks execute, they may attempt to access hci_conn pointers that have already been freed or reallocated, leading to undefined behavior and potential privilege escalation. This vulnerability directly relates to common weakness enumeration CWE-416 which identifies use-after-free conditions in memory management operations. The improper handling of reference counts creates a race condition scenario where multiple threads might simultaneously access or destroy the same connection object without proper synchronization.
The operational impact of this vulnerability extends beyond simple memory corruption, potentially allowing attackers to execute arbitrary code with kernel privileges. When hci_conn lookups occur without appropriate locking mechanisms, concurrent access patterns can result in inconsistent state information and memory dereference errors. The requirement to hold hdev->lock when accessing conn->state demonstrates the need for proper mutex acquisition during critical section execution, aligning with ATT&CK technique T1068 which focuses on local privilege escalation through kernel vulnerabilities. This flaw particularly affects systems running Linux kernels with Bluetooth functionality where multiple concurrent operations might occur simultaneously.
Mitigation strategies must implement comprehensive reference counting mechanisms throughout the Bluetooth management interface, ensuring that hci_conn objects remain valid during callback execution. Proper locking protocols should be enforced around all hci_conn access points, with appropriate use of rcu_read_lock and rcu_read_unlock functions to protect RCU-protected data structures. The fix requires maintaining reference counts for hci_conn pointers stored in mgmt_pending_cmd structures and implementing proper synchronization primitives to prevent concurrent access patterns that could lead to memory corruption. Additionally, all accesses to conn->state must ensure hdev->lock is properly acquired, establishing a consistent pattern for protecting shared kernel data structures. Organizations should prioritize applying kernel updates that implement these reference counting and locking mechanisms to prevent exploitation of this vulnerability across their infrastructure.