CVE-2026-53198High· 8.8▾ TwilightIn the Linux kernel, the following vulnerability has been resolved: ksmbd: fix use-after-free of a deferred file_lock on double SMB2_CANCEL A deferred byte-range lock (an SMB2_LOCK that blocks) registers an async work on conn->async_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 Aug 1.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via NVD
0.4%
0.4% → 0.6%
Last analysed / modified upstream
In the Linux kernel, the following vulnerability has been resolved:
ksmbd: fix use-after-free of a deferred file_lock on double SMB2_CANCEL
A deferred byte-range lock (an SMB2_LOCK that blocks) registers an async work on conn->async_requests via setup_async_work(), with cancel_fn = smb2_remove_blocked_lock and cancel_argv[0] pointing at the struct file_lock.
When the request is cancelled, the worker frees the file_lock with locks_free_lock() and takes the cancelled early-exit, which "goto out"s and never reaches release_async_work() -- the only site that unlinks the work from conn->async_requests and clears cancel_fn/cancel_argv. The work therefore stays matchable on async_requests with a live cancel_fn pointing at the freed file_lock, until connection teardown finally runs release_async_work().
smb2_cancel() fires cancel_fn unconditionally with no state guard, so a second SMB2_CANCEL for the same AsyncId, arriving in that window, re-runs smb2_remove_blocked_lock() on the freed file_lock -- a slab use-after-free:
BUG: KASAN: slab-use-after-free in __locks_delete_block __locks_delete_block locks_delete_block ksmbd_vfs_posix_lock_unblock smb2_remove_blocked_lock smb2_cancel <- 2nd SMB2_CANCEL fires cancel_fn handle_ksmbd_work Allocated by ...: locks_alloc_lock <- smb2_lock Freed by ...: locks_free_lock <- smb2_lock (cancelled branch) ... cache file_lock_cache of size 192
Reproduced on mainline with KASAN by an authenticated SMB client.
Skip a work whose state is already KSMBD_WORK_CANCELLED so its cancel callback cannot be fired a second time.
linux_kernel >= 5.15, < 6.1.176linux_kernel >= 6.2, < 6.6.143linux_kernel >= 6.7, < 6.12.94linux_kernel >= 6.13, < 6.18.36linux_kernel >= 6.19, < 7.0.13linux_kernel = 7.1Upgrade past the affected range:
linux_kernel 7.0.13Connected by shared product, vendor, weakness, or advisory.
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