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CVE-2026-64396

HIGH 8.8 ALL-YEARS

Published 2026-07-25 · Last modified 2026-08-17 · Linux · NVD: Analyzed

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().

ELEVATED IMPACT

Severe if exploited (CVSS 8.8), but no confirmed exploitation. Patch on a normal cadence.

Exploitation likelihood

0.4%chance of exploitation in 30 days · 38th percentile

○ In CISA KEV○ Catalogued PoC

Impact if exploited

8.8CVSS 3.1 · HIGH · CNA

  • ConfidentialityHigh
  • IntegrityHigh
  • AvailabilityHigh

What an attacker needs

  • ✓Access: Reachable over the network — no local access needed
  • ⚠Privileges: Requires a low-privilege account
  • ✓User interaction: No user interaction needed
  • ✓Complexity: No special conditions — reliably repeatable

✓ lowers the bar for an attacker · ⚠ raises it

Proof of concept

No public PoC is currently catalogued.

Search for new PoCs

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Tracked sources are checked weekly for the full archive, including PoCs published after the original disclosure. A later release appears after a tracked source lists it and a refresh succeeds.

Affected

Vendors Linux

Products Linux Linux Kernel

Weakness (CWE)

  • CWE-416: Use after free

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

References and research data (JSON)

Vendor product assessments

Showing 32 of 275 vendor product statements; 243 omitted. Read the full vendor advisory.

  • kernel as a component of Red Hat Enterprise Linux 10 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel

    Red Hat · CVE-2026-64396 · Updated 2026-10-16T23:11:12+00:00
  • kernel-64k-debug-modules-extra as a component of Red Hat Enterprise Linux 10 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel-64k-debug-modules-extra

    Red Hat · CVE-2026-64396 · Updated 2026-10-16T23:11:12+00:00
  • kernel-debug-core as a component of Red Hat Enterprise Linux 10 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel-debug-core

    Red Hat · CVE-2026-64396 · Updated 2026-10-16T23:11:12+00:00
  • kernel-doc as a component of Red Hat Enterprise Linux 10 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel-doc

    Red Hat · CVE-2026-64396 · Updated 2026-10-16T23:11:12+00:00
  • kernel-rt-64k-core as a component of Red Hat Enterprise Linux 10 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel-rt-64k-core

    Red Hat · CVE-2026-64396 · Updated 2026-10-16T23:11:12+00:00
  • kernel-rt-64k-modules-core as a component of Red Hat Enterprise Linux 10 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel-rt-64k-modules-core

    Red Hat · CVE-2026-64396 · Updated 2026-10-16T23:11:12+00:00
  • kernel-rt-debug-modules-extra as a component of Red Hat Enterprise Linux 10 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel-rt-debug-modules-extra

    Red Hat · CVE-2026-64396 · Updated 2026-10-16T23:11:12+00:00
  • kernel-uki-virt as a component of Red Hat Enterprise Linux 10 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel-uki-virt

    Red Hat · CVE-2026-64396 · Updated 2026-10-16T23:11:12+00:00
  • kernel.src as a component of Red Hat Enterprise Linux 10 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel?arch=src

    Red Hat · CVE-2026-64396 · Updated 2026-10-16T23:11:12+00:00
  • kernel-debug as a component of Red Hat Enterprise Linux 6 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel-debug

    Red Hat · CVE-2026-64396 · Updated 2026-10-16T23:11:12+00:00
  • kernel.src as a component of Red Hat Enterprise Linux 6 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel?arch=src

    Red Hat · CVE-2026-64396 · Updated 2026-10-16T23:11:12+00:00
  • kernel-devel as a component of Red Hat Enterprise Linux 7 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel-devel

    Red Hat · CVE-2026-64396 · Updated 2026-10-16T23:11:12+00:00
  • kernel-rt-devel as a component of Red Hat Enterprise Linux 7 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel-rt-devel

    Red Hat · CVE-2026-64396 · Updated 2026-10-16T23:11:12+00:00
  • kernel-tools-libs-devel as a component of Red Hat Enterprise Linux 7 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel-tools-libs-devel

    Red Hat · CVE-2026-64396 · Updated 2026-10-16T23:11:12+00:00
  • kernel-cross-headers as a component of Red Hat Enterprise Linux 8 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel-cross-headers

    Red Hat · CVE-2026-64396 · Updated 2026-10-16T23:11:12+00:00
  • kernel-headers as a component of Red Hat Enterprise Linux 8 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel-headers

    Red Hat · CVE-2026-64396 · Updated 2026-10-16T23:11:12+00:00
  • kernel-rt-debug-core as a component of Red Hat Enterprise Linux 8 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel-rt-debug-core

    Red Hat · CVE-2026-64396 · Updated 2026-10-16T23:11:12+00:00
  • kernel-rt-modules-extra as a component of Red Hat Enterprise Linux 8 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel-rt-modules-extra

    Red Hat · CVE-2026-64396 · Updated 2026-10-16T23:11:12+00:00
  • kernel-zfcpdump-core as a component of Red Hat Enterprise Linux 8 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel-zfcpdump-core

    Red Hat · CVE-2026-64396 · Updated 2026-10-16T23:11:12+00:00
  • kernel as a component of Red Hat Enterprise Linux 9 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel

    Red Hat · CVE-2026-64396 · Updated 2026-10-16T23:11:12+00:00
  • kernel-64k-debug-modules-extra as a component of Red Hat Enterprise Linux 9 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel-64k-debug-modules-extra

    Red Hat · CVE-2026-64396 · Updated 2026-10-16T23:11:12+00:00
  • kernel-64k-modules-partner as a component of Red Hat Enterprise Linux 9 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel-64k-modules-partner

    Red Hat · CVE-2026-64396 · Updated 2026-10-16T23:11:12+00:00
  • kernel-debug-modules as a component of Red Hat Enterprise Linux 9 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel-debug-modules

    Red Hat · CVE-2026-64396 · Updated 2026-10-16T23:11:12+00:00
  • kernel-doc as a component of Red Hat Enterprise Linux 9 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel-doc

    Red Hat · CVE-2026-64396 · Updated 2026-10-16T23:11:12+00:00
  • kernel-rt-64k as a component of Red Hat Enterprise Linux 9 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel-rt-64k

    Red Hat · CVE-2026-64396 · Updated 2026-10-16T23:11:12+00:00
  • kernel-rt-64k-debug-modules-extra as a component of Red Hat Enterprise Linux 9 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel-rt-64k-debug-modules-extra

    Red Hat · CVE-2026-64396 · Updated 2026-10-16T23:11:12+00:00
  • kernel-rt-64k-modules-internal as a component of Red Hat Enterprise Linux 9 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel-rt-64k-modules-internal

    Red Hat · CVE-2026-64396 · Updated 2026-10-16T23:11:12+00:00
  • kernel-rt-debug-modules-core as a component of Red Hat Enterprise Linux 9 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel-rt-debug-modules-core

    Red Hat · CVE-2026-64396 · Updated 2026-10-16T23:11:12+00:00
  • kernel-rt-modules-core as a component of Red Hat Enterprise Linux 9 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel-rt-modules-core

    Red Hat · CVE-2026-64396 · Updated 2026-10-16T23:11:12+00:00
  • kernel-tools-libs-devel as a component of Red Hat Enterprise Linux 9 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel-tools-libs-devel

    Red Hat · CVE-2026-64396 · Updated 2026-10-16T23:11:12+00:00
  • kernel-zfcpdump-modules-extra as a component of Red Hat Enterprise Linux 9 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel-zfcpdump-modules-extra

    Red Hat · CVE-2026-64396 · Updated 2026-10-16T23:11:12+00:00
  • rv as a component of Red Hat Enterprise Linux 9 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/rv

    Red Hat · CVE-2026-64396 · Updated 2026-10-16T23:11:12+00:00

Known Affected Software Configurations

VendorProductVersion range
LinuxLinux Kernel≥ 5.15 and < 6.1.178
LinuxLinux Kernel≥ 6.2 and < 6.6.145
LinuxLinux Kernel≥ 6.7 and < 6.12.96
LinuxLinux Kernel≥ 6.13 and < 6.18.39
LinuxLinux Kernel≥ 6.19 and < 7.1.4

All CVSS metrics

  • HIGH 8.8 v3.1 · CNA Primary
    CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
  • HIGH 8.8 v3.1 · NVD Secondary
    CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

References

Patches & mitigations

Advisories

Technical & other

Sources: NVD · CVE.org · All sources and attribution · EPSS