# CVE-2026-64396: linux: In the Linux kernel, the following vulnerability has been resolved:  ksmbd: fix UAF of struct file_lock in SMB2_LOCK...

CVE-2026-64396 is fixed in 2 products on 1 platform, first by DEBIAN-CVE-2026-64396, released July 26, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-64396
- Priority: High
- CVSS: 8.8 (high)
- EPSS: 0.0044
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jul 25, 2026

## 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().

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 6.1.180-1 | [DEBIAN-CVE-2026-64396](https://patchblox.com/security/data/fix/linux/debian-cve-2026-64396.md) | Jul 26, 2026 |
| Linux | linux Debian 13.5 (trixie) | 6.12.96-1 | [DEBIAN-CVE-2026-64396](https://patchblox.com/security/data/fix/linux/debian-cve-2026-64396.md) | Jul 26, 2026 |
| Linux | linux Debian 14 | 7.1.4-1 | [DEBIAN-CVE-2026-64396](https://patchblox.com/security/data/fix/linux/debian-cve-2026-64396.md) | Jul 26, 2026 |
| Linux | linux-6.12 Debian 12.15 (bookworm) | 6.12.100-1~deb12u1 | [DEBIAN-CVE-2026-64396](https://patchblox.com/security/data/fix/linux/debian-cve-2026-64396.md) | Jul 26, 2026 |

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Data as of 2026-11-08T06:59:42Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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