High severity · published Jul 25, 2026
CVE-2026-64396
ksmbd: fix UAF of struct file_lock in SMB2_LOCK deferred-lock cancellation
8.8
CVSS
0.4%
EPSS
No
On KEV
Description
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().
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 38% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
KE
Kernel · Linux
5.15 before 6.1.178; 6.2 before 6.6.145; 6.7 before 6.12.96; 6.13 before 6.18.39; 6.19 before 7.1.4 · source: NVD
LI
Linux · Linux
e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 before 367c42a611fe488b7b03f1f6737f4dee0e8b20a2; e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 before 7703fd9aba1f2483c8e55f9ff73b7663e0761ed9; e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 before 463bbd79698513af4dad50fe1c573825f297ca2e; e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 before 5aa1cb01155f96824003baf7997cdf1f150caba3; e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 before 5c75275c0fc9a2deb0d8f5604edcb16f288171c8; e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 before d20d1c8ba5765d1d12eefc0aee6385ab3f240e1e; +1 more · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-64396
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-64396
Patch
https://git.kernel.org/stable/c/367c42a611fe488b7b03f1f6737f4dee0e8b20a2
Patch
https://git.kernel.org/stable/c/463bbd79698513af4dad50fe1c573825f297ca2e
Patch
https://git.kernel.org/stable/c/5aa1cb01155f96824003baf7997cdf1f150caba3
Patch
https://git.kernel.org/stable/c/5c75275c0fc9a2deb0d8f5604edcb16f288171c8
Patch
https://git.kernel.org/stable/c/7703fd9aba1f2483c8e55f9ff73b7663e0761ed9
Patch
https://git.kernel.org/stable/c/d20d1c8ba5765d1d12eefc0aee6385ab3f240e1e
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