CVE-2026-64396High· 8.8▾ TwilightIn the Linux kernel, the following vulnerability has been resolved: ksmbd: fix UAF of struct file_lock in SMB2_LOCK deferred-lock cancellation When a blocking byte-range lock request is deferred in the FILE_LOCK_DEFERRED path, ksmbd re…
▾ Twilight zone — High severity, or a signal on a lesser flaw
impact 48.4 · likelihood 0.1 · exploitation 0
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Exploit-prediction probability, daily snapshots since Sep 5.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via NVD
Last analysed / modified upstream
0.4%
0.4% → 0.6%
In the Linux kernel, the following vulnerability has been resolved:
ksmbd: fix UAF of struct file_lock in SMB2_LOCK deferred-lock cancellation
When a blocking byte-range lock request is deferred in the FILE_LOCK_DEFERRED path, ksmbd registers the asynchronous work into the connection's async_requests list via setup_async_work(). The cancel callback smb2_remove_blocked_lock() holds a reference to the flock.
If the lock waiter is subsequently woken up but the work state is no longer KSMBD_WORK_ACTIVE (e.g., due to a concurrent cancellation), the cleanup path calls locks_free_lock(flock) without dequeuing the work from the async_requests list. Concurrently, smb2_cancel() walks the list under conn->request_lock and invokes the cancel callback, which then dereferences the already freed 'flock'. This leads to a slab-use-after-free inside __wake_up_common.
Fix this by restructuring the cleanup logic after the worker returns from ksmbd_vfs_posix_lock_wait(). Move list_del(&smb_lock->llist) and release_async_work(work) to the top of the cleanup block. This guarantees that the async work is completely dequeued and serialized under conn->request_lock before locks_free_lock(flock) is called, rendering the flock unreachable for any concurrent smb2_cancel().
linux_kernel >= 5.15, < 6.1.178linux_kernel >= 6.2, < 6.6.145linux_kernel >= 6.7, < 6.12.96linux_kernel >= 6.13, < 6.18.39linux_kernel >= 6.19, < 7.1.4Upgrade past the affected range:
linux_kernel 7.1.4Connected by shared product, vendor, weakness, or advisory.
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