[CVE-2026-74614][MODERATE 7.0] vsock/virtio: read virtqueues under worker locks

[AL-KERNEL <alkernel@kernelcve.org>]

CVE: CVE-2026-74614
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: vsock/virtio: read virtqueues under worker locks
Commit: 941329ce14c5f481223a10d1d4c8b57ea7f3048a
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=941329ce14c5f481223a10d1d4c8b57ea7f3048a
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74614
Analysis date: Sat, 22 Aug 2026 14:01:18 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum**:: Paranoid handling reaches Actionable Moderate and should not be auto-closed. Conservative handling is borderline manual-review due to race-dependent stale virtqueue lifetime corruption.
Manual review required: YES

Summary:
A race in virtio-vsock suspend/resume handling can leave worker threads using a stale deleted virtqueue pointer, causing at least a local guest kernel crash and requiring manual review for possible UAF impact beyond DoS.

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ABOUT THIS REPORT
======================================================================

The original Linux kernel CVE announcement for CVE-2026-74614 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74614

The original announcement does not normally provide a security severity
estimate, CVSS assessment, or enough information to determine whether the
reported kernel bug represents a practically relevant security issue.

This report was generated by AL-KERNEL, an AI-assisted Linux kernel
vulnerability analysis system developed by Alexander Larkin. It combines
an autonomous classifier with LLM-assisted technical analysis and a
separate ActionableScore mechanism.

The purpose of this report is to prioritize Linux kernel CVEs before
manual review, identify cases that require prompt investigation, and
support automatic closure of issues that are unlikely to have meaningful
security impact.

Published priority for this report: MODERATE 7.0
Manual review required: YES

A detailed explanation of the methodology and priority rules is included
at the end of this message.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-74614	MODERATE	CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';*CWE-416;CWE-362;CWE-667;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'A race in virtio vsock workers can leave TX, RX, or event work using a stale virtqueue pointer across device suspend and resume. The worker reads the virtqueue before taking the worker mutex and before checking the run flag, so a delayed worker can keep a pointer to a deleted queue while restore installs a replacement queue and sets the run state again. This can result in a use after free when the worker later calls virtqueue operations on the stale object, causing at least a kernel crash and denial of service. For the CVSS the PR:L is used for the paranoid score because a local user or local process in the guest may be able to generate vsock activity needed to exercise the worker path, while the suspend resume timing still makes exploitation race dependent. The issue is not directly reachable over a normal IP network and requires a virtio vsock virtualization context. Impact is at least local denial of service, and in the worst case may allow confidentiality or integrity impact due to kernel use after free behavior, so manual review is recommended.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 5)	YES	LOCK VIRT SIMPLEFIX HARDWARE LINUS  KPANIC INCREASED_TO_MODERATE_FROM_LOW_BASED_ON_GUESSCVSS	YES	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=5
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: **4**
* Paranoid score: **5**
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**:: Paranoid handling reaches Actionable Moderate and should not be auto-closed. Conservative handling is borderline manual-review due to race-dependent stale virtqueue lifetime corruption.

## 2. Signal breakdown

Paranoid score calculation:

* **Local unprivileged trigger: +1**
  A local process in the guest may be able to generate virtio-vsock RX/TX/event activity and keep worker paths active, although suspend/resume timing is a separate precondition.

* **Memory corruption, weak/indirect corruption candidate: +1**
  The worker can retain a pointer to a deleted virtqueue. This is a stale pointer / UAF candidate, but the patch does not show attacker-controlled reclaim, type confusion, callback control, or write-after-free.

* **Real lifetime corruption: +1**
  The bug is explicitly about using a deleted virtqueue generation after restore installs replacement queues.

* **Reliable kernel crash / strong DoS: +1**
  Calling virtqueue operations on a deleted queue is a credible kernel crash path.

* **Privileged kernel/device-management lifetime path: +1**
  The corruption occurs in virtio device suspend/resume queue replacement, a trusted kernel device-management path.

* **Common virtualization transport exposure: +1**
  virtio-vsock is a common VM transport in virtualization environments, although not a normal Internet-facing networking path.

* **Hard or unreliable race / special timing required: -1**
  Triggering requires a worker delayed across freeze/restore and matching queue-generation timing.

Conservative score excludes one exposure/device-management elevation, giving **4**.

## 3. Reachability analysis

The bug is not reachable over a normal IP network. It requires a virtio-vsock environment and a suspend/resume or restore event that replaces virtqueues. A local guest process may be able to generate vsock traffic and exercise TX, RX, or event workers, but reliable triggering depends on timing against device freeze/restore, which is not usually fully controlled by an unprivileged user.

Namespaces and containers may matter if AF_VSOCK is exposed inside a container, but the suspend/resume transition remains outside ordinary namespace control. This is not a default exposure on all Linux systems, but it is relevant for VM guests using virtio-vsock.

Call-site confidence: **high**, because the patch shows the affected TX, RX, and event worker call paths and the stale virtqueue read is directly visible.

## 4. Severity interpretation

This behaves like an **Actionable Moderate** issue, with **Important-candidate review value** in paranoid triage because it is a real kernel lifetime bug involving a stale virtqueue pointer. The realistic demonstrated impact is kernel crash / DoS. Theoretical confidentiality or integrity impact is weaker because the patch does not show attacker-controlled reclaim, object replacement, callback dispatch, or an arbitrary write primitive.

Under the race-UAF downgrade rule, this should not be automatically treated as strong LPE. It should still receive manual review because stale virtqueue lifetime bugs in virtualization transports can be underestimated during initial triage.

## 5. One-sentence report phrase

A race in virtio-vsock suspend/resume handling can leave worker threads using a stale deleted virtqueue pointer, causing at least a local guest kernel crash and requiring manual review for possible UAF impact beyond DoS.

## 6. Manual review recommendation

**MANUAL CHECK REQUIRED. YES REQUIRES MANUAL CHECK.**

Reason: this is a race-dependent stale pointer / UAF candidate in a virtualization transport path. The proven impact is DoS, but the lifetime-corruption class and virtqueue operations on deleted objects justify manual review rather than auto-closure.

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UPSTREAM PATCH SUMMARY
======================================================================

Patch: vsock/virtio: read virtqueues under worker locks
Commit: 941329ce14c5f481223a10d1d4c8b57ea7f3048a
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=941329ce14c5f481223a10d1d4c8b57ea7f3048a

Commit description:

Commit bd50c5d ("vsock/virtio: add support for device
suspend/resume") made the *_run flags transition from false to true when
restore installs replacement virtqueues.  The RX, TX and event workers
read their virtqueue before locking and checking the corresponding flag,
so a worker delayed across freeze and restore can observe the replacement
queue's running state while retaining a pointer to the deleted queue.

Read each virtqueue under its mutex after checking the run flag, keeping
the pointer and state in the same queue generation.

Fixes: bd50c5d ("vsock/virtio: add support for device suspend/resume")
Cc: stable@vger.kernel.org
Reported-by: Xiang Mei <xmei5@asu.edu>
Link: https://lore.kernel.org/r/20260727035804.1860862-1-bestswngs@gmail.com
Signed-off-by: Weiming Shi <bestswngs@gmail.com>
Reviewed-by: Bobby Eshleman <bobbyeshleman@meta.com>
Link: https://patch.msgid.link/e79f68ad9284c983364fc3ac46904b6d9ef50231.1785352330.git.bestswngs@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  net/vmw_vsock/virtio_transport.c

Diff excerpt:

Not included in this email. See the upstream URL for the full patch.

Full patch:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=941329ce14c5f481223a10d1d4c8b57ea7f3048a

======================================================================
DETAILED REPORT METHODOLOGY
======================================================================

The original Linux kernel CVE announcement for CVE-2026-74614 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74614

The original CVE announcement normally does not include a security-level
estimate. In particular, it may not contain a CVSS assessment, an impact
level, or enough information to determine whether the reported bug is a
practically relevant security issue. One purpose of this parallel CVE list
is to provide that missing technical and prioritization information.

The original goal of the AL-KERNEL project was to prioritize Linux kernel
CVE analysis automatically before manual review. The system can also help
identify non-security issues that may be suitable for automatic closure.

This report was generated by AL-KERNEL, an AI-assisted Linux kernel
vulnerability analysis system developed by Alexander Larkin.

The first analysis stage combines an autonomous classifier with additional
LLM-based analysis. The autonomous classifier runs locally on a CPU and is
based on a backpropagation neural network. Together, these mechanisms
produce a technical vulnerability description, identify likely weakness
types, estimate CVSS severity, and provide input for ActionableScore.

Two CVSS estimates are retained because incomplete kernel vulnerability
information often permits more than one defensible interpretation:

  Conservative CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 7

The conservative vector represents a lower-impact interpretation.
The Best/paranoid vector intentionally represents a plausible upper-bound
interpretation and should not automatically be treated as demonstrated
real-world impact.

CVSS may also need to be adjusted for a particular Linux deployment,
because actual reachability, privileges, enabled kernel configuration,
hardware, namespaces, exposed device nodes, and other environmental
conditions can differ significantly between systems.

A separate ActionableScore mechanism evaluates practical remediation
urgency. Its analysis may include reachability, attack prerequisites,
subsystem exposure, memory-corruption characteristics, denial-of-service
reliability, and possible confidentiality, integrity, or
privilege-escalation impact.

  Conservative ActionableScore: 4
  Paranoid ActionableScore: 5

The final base severity is taken directly from the second tab-separated
field of the AL-KERNEL classification result. ActionableScore does not
replace or independently override that final AL-KERNEL decision, and
if ActionableScore adjusted impact level of ALKERNEL, then you would see
self-readable flags above like INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7.

For an AL-KERNEL result of MODERATE, this report uses the following
additional presentation split:

  ActionableScore below 5   -> MODERATE REGULAR
  ActionableScore 5 or more -> MODERATE 7.0

The distinction between MODERATE REGULAR and MODERATE 7.0 makes it
possible to identify Moderate issues that should receive manual analysis
and fixes before lower-priority MODERATE REGULAR issues. In many cases,
MODERATE REGULAR fixes may wait for a later rebase or routine update.

There is one override in which MODERATE REGULAR becomes MODERATE 7.0
even when the ActionableScore is below 5. When the AL-KERNEL result
contains the KPANIC flag, a MODERATE result is always presented as
MODERATE 7.0. The KPANIC flag selected with few regexps without
usage of AI at all, so it helps to detect cases when Kernel Crash happens
and similar (to filter False-Negative results from the LLM usage).

KPANIC indicates that a reliable kernel crash, kernel panic, or similarly
serious kernel availability impact was identified by the classification
workflow.

AL-KERNEL base severity for this report: MODERATE
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): MODERATE 7.0

These results are intended to support engineering triage. They are
machine-generated estimates, and cases marked for manual review should
be validated by a human security engineer before final disposition.
For more info read docs linked from here: https://kernelcve.org/
(and you can submit you own patch there to generate such a report
for non-existant CVE-id yet).

Note that in many cases this AI tool selects higher severity, than
real is (means you can expect Importants instead of Moderate 7.0 or
Moderates 7.0 instead of regular Moderates). If you see such cases,
please use reply email interface to add additional manual analyses
info to this particular CVE.
And please, please, let me know when you see Lows instead of Importants
or Important instead of Low (because particular for such cases I
need to tune this AI tool to make it better for this one and next similar).
My contact email for such notifications is alexanjelausa@gmail.com (and both
send reply to CVE record itself too and see "reply" button below for howto reply).