0.0
NA
CVE-2026-64396
ksmbd: fix UAF of struct file_lock in SMB2_LOCK deferred-lock cancellation
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().

INFO

Published Date :

July 25, 2026, 10:17 a.m.

Last Modified :

July 25, 2026, 10:17 a.m.

Remotely Exploit :

No

Source :

416baaa9-dc9f-4396-8d5f-8c081fb06d67
Affected Products

The following products are affected by CVE-2026-64396 vulnerability. Even if cvefeed.io is aware of the exact versions of the products that are affected, the information is not represented in the table below.

ID Vendor Product Action
1 Linux linux_kernel
Solution
Fix a use-after-free by ensuring work is dequeued before freeing lock.
  • Update the Linux kernel.
  • Ensure work is dequeued before freeing lock.
  • Serialize cleanup under request lock.
  • Apply the provided kernel patch.
CWE - Common Weakness Enumeration

While CVE identifies specific instances of vulnerabilities, CWE categorizes the common flaws or weaknesses that can lead to vulnerabilities. CVE-2026-64396 is associated with the following CWEs:

Common Attack Pattern Enumeration and Classification (CAPEC)

Common Attack Pattern Enumeration and Classification (CAPEC) stores attack patterns, which are descriptions of the common attributes and approaches employed by adversaries to exploit the CVE-2026-64396 weaknesses.

We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).

Results are limited to the first 15 repositories due to potential performance issues.

The following list is the news that have been mention CVE-2026-64396 vulnerability anywhere in the article.

The following table lists the changes that have been made to the CVE-2026-64396 vulnerability over time.

Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.

  • New CVE Received by 416baaa9-dc9f-4396-8d5f-8c081fb06d67

    Jul. 25, 2026

    Action Type Old Value New Value
    Added Affected [{'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': '1da177e4c3f41524e886b7f1b8a0c1fc7321cac2', 'lessThan': '367c42a611fe488b7b03f1f6737f4dee0e8b20a2', 'versionType': 'git'}, {'status': 'affected', 'version': '1da177e4c3f41524e886b7f1b8a0c1fc7321cac2', 'lessThan': '7703fd9aba1f2483c8e55f9ff73b7663e0761ed9', 'versionType': 'git'}, {'status': 'affected', 'version': '1da177e4c3f41524e886b7f1b8a0c1fc7321cac2', 'lessThan': '463bbd79698513af4dad50fe1c573825f297ca2e', 'versionType': 'git'}, {'status': 'affected', 'version': '1da177e4c3f41524e886b7f1b8a0c1fc7321cac2', 'lessThan': '5aa1cb01155f96824003baf7997cdf1f150caba3', 'versionType': 'git'}, {'status': 'affected', 'version': '1da177e4c3f41524e886b7f1b8a0c1fc7321cac2', 'lessThan': '5c75275c0fc9a2deb0d8f5604edcb16f288171c8', 'versionType': 'git'}, {'status': 'affected', 'version': '1da177e4c3f41524e886b7f1b8a0c1fc7321cac2', 'lessThan': 'd20d1c8ba5765d1d12eefc0aee6385ab3f240e1e', 'versionType': 'git'}, {'status': 'affected', 'version': '0', 'lessThan': '6.1.178', 'versionType': 'semver'}, {'status': 'affected', 'version': '0', 'lessThan': '6.6.145', 'versionType': 'semver'}, {'status': 'affected', 'version': '0', 'lessThan': '6.12.96', 'versionType': 'semver'}, {'status': 'affected', 'version': '0', 'lessThan': '6.18.39', 'versionType': 'semver'}, {'status': 'affected', 'version': '0', 'lessThan': '7.1.4', 'versionType': 'semver'}], 'programFiles': ['fs/smb/server/smb2pdu.c'], 'defaultStatus': 'unaffected'}, {'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'unaffected', 'version': '6.1.178', 'versionType': 'semver', 'lessThanOrEqual': '6.1.*'}, {'status': 'unaffected', 'version': '6.6.145', 'versionType': 'semver', 'lessThanOrEqual': '6.6.*'}, {'status': 'unaffected', 'version': '6.12.96', 'versionType': 'semver', 'lessThanOrEqual': '6.12.*'}, {'status': 'unaffected', 'version': '6.18.39', 'versionType': 'semver', 'lessThanOrEqual': '6.18.*'}, {'status': 'unaffected', 'version': '7.1.4', 'versionType': 'semver', 'lessThanOrEqual': '7.1.*'}, {'status': 'unaffected', 'version': '7.2-rc1', 'versionType': 'original_commit_for_fix', 'lessThanOrEqual': '*'}], 'programFiles': ['fs/smb/server/smb2pdu.c'], 'defaultStatus': 'affected'}]
    Added 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().
    Added Reference https://git.kernel.org/stable/c/367c42a611fe488b7b03f1f6737f4dee0e8b20a2
    Added Reference https://git.kernel.org/stable/c/463bbd79698513af4dad50fe1c573825f297ca2e
    Added Reference https://git.kernel.org/stable/c/5aa1cb01155f96824003baf7997cdf1f150caba3
    Added Reference https://git.kernel.org/stable/c/5c75275c0fc9a2deb0d8f5604edcb16f288171c8
    Added Reference https://git.kernel.org/stable/c/7703fd9aba1f2483c8e55f9ff73b7663e0761ed9
    Added Reference https://git.kernel.org/stable/c/d20d1c8ba5765d1d12eefc0aee6385ab3f240e1e
EPSS is a daily estimate of the probability of exploitation activity being observed over the next 30 days. Following chart shows the EPSS score history of the vulnerability.