CVE-2026-64340: USB: legousbtower: fix use-after-free on disconnect race
In the Linux kernel, the following vulnerability has been resolved:
USB: legousbtower: fix use-after-free on disconnect race
mutexunlock() 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 mutexunlock() when release() races with disconnect().
[1] a51749ab34d9 ("locking/mutex: Document that mutexunlock() is non-atomic") [2] 2b9d9e0a9ba0 ("locking/mutex: Clarify that mutexunlock(), and most other sleeping locks, can still use the lock object after it's unlocked")
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
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ubuntu/linux-riscvto a version that resolves this vulnerability.Fixed in 7.0.0-31.31.1 - Compensating control
Use a kref to manage and release the USB legousbtower driver data lifetime, preventing use-after-free when release() races with disconnect() and mutex_unlock() may still access the mutex structure.
Event History
Frequently Asked Questions
What conditions are required to trigger this issue?
The race requires the LEGO USB Tower driver data to be released while a USB device disconnect occurs. Exploitation requires local access and low privileges; no user interaction is required according to the CVSS vector.
Who is most likely exposed?
Systems running the Linux kernel with the legousbtower USB driver in use are the relevant population. The issue is tied to device disconnect handling, so exposure depends on use of the affected USB driver and a disconnect race.
What change resolves the vulnerability?
The resolved fix uses a kref to manage the driver-data lifetime, preventing the data from being freed while mutex_unlock() may still access its mutex structure.