CVE-2026-90253 in Linux
Summary
by MITRE • 09/17/2026
In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: MGMT: free the mesh send cancel command when it is cancelled
mesh_send_cancel() queues the pending command with a NULL destroy callback, so it is only freed if send_cancel() runs. A cancelled entry is leaked, as _hci_cmd_sync_cancel_entry() does not release entry->data when there is no destroy callback, and hci_cmd_sync_clear() cancels every pending entry when the controller is unregistered. Nothing else reclaims it either: mgmt_pending_new() does not put the command on hdev->mgmt_pending.
The leak also pins the socket reference taken by mgmt_pending_new(), so the mgmt socket is never released.
Free the command from a destroy callback.
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Analysis
by VulDB Data Team • 09/17/2026
This vulnerability represents a resource management flaw within the Linux kernel Bluetooth subsystem, specifically affecting the Management Interface (MGMT) layer used for controlling and monitoring Bluetooth devices. The core issue stems from an incorrect handling of pending commands during cancellation operations in the mesh send cancel functionality. When a command is queued via mesh_send_cancel(), it is registered with a NULL destroy callback pointer. This design choice creates a critical dependency on external cleanup mechanisms that fail to execute under specific conditions, leading to memory leaks and persistent socket references that prevent proper resource release.
The technical flaw occurs because the kernel's command synchronization framework relies on destroy callbacks to free associated data structures when commands are cancelled or completed normally. In this case, since mesh_send_cancel() explicitly passes a NULL pointer for the destroy callback, the standard cleanup path is bypassed. When hci_cmd_sync_clear() executes during controller unregistration, it iterates through all pending entries and cancels them. However, because _hci_cmd_sync_cancel_entry() checks for the presence of a valid destroy callback before freeing entry->data, the absence of such a callback results in the command data structure remaining allocated in memory. This is compounded by the fact that mgmt_pending_new(), which initially allocates these structures, does not place them on the hdev->mgmt_pending list when they are intended for cancellation-only scenarios, leaving no other mechanism to reclaim this memory.
The operational impact of this vulnerability extends beyond simple memory exhaustion. The leaked command structure also holds a reference count on the underlying mgmt socket. Because the destroy callback is never invoked to decrement this reference, the socket remains open and active even after it should have been closed or when the associated device context is being torn down. This prevents the proper release of network resources within the kernel, potentially leading to resource starvation in systems with frequent Bluetooth controller registration and unregistration cycles. Over time, these accumulated leaks can degrade system performance, cause instability in Bluetooth stack operations, and increase the attack surface by leaving sensitive socket structures accessible longer than intended.
From a classification perspective, this issue aligns with CWE-401, which describes missing release of memory after effective lifetime, as well as CWE-772, referring to Missing Release of Resource after Effective Lifetime. In terms of adversary behavior and defensive mapping, the persistence of these resources could be leveraged in denial-of-service scenarios by exhausting kernel memory or socket handles, corresponding to ATT&CK technique T1496, Resource Hijacking. The vulnerability highlights a common pitfall in driver development where error paths or cancellation logic are not fully synchronized with allocation strategies.
To mitigate this issue, the primary remediation involves modifying the mesh_send_cancel() function to ensure that every allocated command structure has an associated destroy callback registered within the kernel's pending command framework. This ensures that when hci_cmd_sync_clear() cancels entries during controller unregistration, the corresponding data structures are properly freed and socket references are correctly decremented. Developers should audit similar patterns in the Bluetooth stack where commands might be queued without proper lifecycle management callbacks to prevent recurrence of this resource leak pattern across other subsystems.