CVE-2026-64344 in Linux
Summary
by MITRE • 07/25/2026
In the Linux kernel, the following vulnerability has been resolved:
USB: idmouse: fix use-after-free on disconnect race
mutex_unlock() may access the mutex structure after releasing the lock and therefore cannot be used to manage lifetime of objects directly (unlike spinlocks and refcounts). [1][2]
Use a kref to release the driver data to avoid use-after-free in mutex_unlock() when release() races with disconnect().
[1] a51749ab34d9 ("locking/mutex: Document that mutex_unlock() is
non-atomic") [2] 2b9d9e0a9ba0 ("locking/mutex: Clarify that mutex_unlock(), and most
other sleeping locks, can still use the lock object after it's unlocked")
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Analysis
by VulDB Data Team • 07/25/2026
The vulnerability identified in the Linux kernel represents a critical use-after-free condition affecting the USB input mouse driver implementation. This flaw occurs during concurrent operations when the disconnect() function executes simultaneously with the release() callback, creating a race condition that can lead to memory corruption and system instability. The issue specifically impacts the idmouse driver component within the USB subsystem where improper synchronization mechanisms are employed to manage object lifetimes.
The technical root cause stems from the incorrect usage of mutex_unlock() for managing object lifetime semantics. Traditional mutex implementations in Linux kernel do not guarantee that the mutex structure remains valid after unlock operations have completed, as documented in kernel commit a51749ab34d9 and further clarified in 2b9d9e0a9ba0. Unlike spinlocks which provide atomic operations suitable for immediate object cleanup or reference counting mechanisms that properly manage object lifecycle, mutex_unlock() can access the mutex structure after releasing the lock, making it unsuitable for direct lifetime management of driver data structures.
This vulnerability directly maps to CWE-416, which describes the use-after-free condition where a program continues to reference memory after it has been freed. The operational impact extends beyond simple memory corruption as the race condition can be exploited to cause system crashes, data loss, or potentially privilege escalation depending on the specific execution context. When concurrent disconnect and release operations occur, the driver data structure may be freed while mutex_unlock() attempts to access it, leading to unpredictable behavior that can compromise system stability.
The resolution implemented addresses this by replacing the problematic synchronization approach with a kref-based reference counting mechanism. This solution ensures proper object lifetime management through kernel's reference counting infrastructure which is designed specifically for handling concurrent access scenarios where objects may be freed by different execution paths. The kref approach provides atomic reference counting operations that prevent premature deallocation while maintaining proper synchronization across concurrent access patterns, eliminating the race condition between disconnect() and release() operations.
From an ATT&CK perspective, this vulnerability could potentially be leveraged as part of a broader exploitation chain targeting kernel memory corruption primitives, though it primarily manifests as a system stability issue rather than direct privilege escalation. The mitigation strategy aligns with defensive programming practices recommended for kernel development, emphasizing the importance of using appropriate synchronization primitives that match their intended use cases. This fix demonstrates the necessity of understanding the semantic differences between various locking mechanisms in kernel space and proper object lifecycle management to prevent subtle but critical race conditions that can compromise system integrity.