[CVE-2026-90142][MODERATE 7.0] virtio_net: Fix resize of the RX ring [ Upstream

[CVE-2026-90142][MODERATE 7.0] virtio_net: Fix resize of the RX ring [ Upstream

[AL-KERNEL]

CVE: CVE-2026-90142
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: virtio_net: Fix resize of the RX ring [ Upstream
Commit: 8344c9233c8f77017174d9e280c5a26034d068b6
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8344c9233c8f77017174d9e280c5a26034d068b6
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90142
Analysis date: Thu, 17 Sep 2026 19:05:12 -0400
ActionableScore: 5
ActionableScore lower bound: unknown
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-90142 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90142

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.

======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-90142	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-90142 CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H';*CWE-787;CWE-122;CWE-131;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7.8';DESCR 'An out of bounds write can occur in virtio_net when an AF_XDP socket is attached and the RX ring is enlarged without resizing the rq xsk_buffs array. After the virtqueue grows, virtnet_rx_resume can use the new ring size and write struct xdp_buff pointers beyond the allocation created for the old ring size. The documented sequence is easily reproducible and does not require a race or a narrow timing window. Impact is at least a local denial of service through kernel memory corruption and a kernel crash. In the worst case, corruption of an adjacent kernel heap object may affect confidentiality and integrity or support privilege escalation, although reliable control of the overwritten object is not established by the supplied code. For the CVSS the PR:L is used in the paranoid score because CAP_NET_ADMIN may be delegated to a container root, network service account, or another restricted local process that does not otherwise have full control of the kernel. The issue is not directly network reachable because an attacker must locally attach an AF_XDP socket and request an RX ring resize. The concrete kernel heap out of bounds write makes additional manual analysis necessary.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5)  SKIP CVE-2026-90142 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES  NO NO unknown 	MAYBE	VIRT NOMEMCHK SIMPLEFIX NETWORK LINUS KPANIC  KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFKP	-	-	checked

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ACTIONABLESCORE ANALYSIS
======================================================================

ActionableScore=5
PrimitiveClass=CLASS_A
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO

1. ActionableScore

* Raw conservative score: 3
* Conservative score: 5
* Raw paranoid score: 3
* Paranoid score: 5
* Applied conservative manual-review safety floor: 3 -> 5
* Applied paranoid manual-review safety floor: 3 -> 5
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::

2. Signal breakdown

* +2 Strong corruption primitive. Increasing the RX ring leaves `rq->xsk_buffs` sized for the old ring, after which `virtnet_rx_resume()` writes multiple `struct xdp_buff` pointers beyond the kernel allocation. The attacker influences the overrun extent through the requested ring size.
* +1 Reliable kernel crash or strong DoS. Repeated pointer-sized writes beyond a kernel array can corrupt adjacent memory and realistically cause an Oops or kernel crash.
* +0 Memory-layout invariant. The allocation-size versus ring-size mismatch is the cause of the established OOB write and is not counted again.
* +0 LPE leverage. The written values are kernel-derived pointers, and controlled victim-object selection, arbitrary data, callback corruption, or credential modification is not demonstrated.
* +0 Confidentiality and integrity consequences. Adjacent kernel memory is corrupted, but no disclosure path or security-sensitive target is established.
* +0 Remote reachability. Network packets alone do not attach AF_XDP or resize the RX ring.
* +0 Local-unprivileged trigger. The complete AF_XDP setup, XDP attachment, and ring-resize sequence is not established as available to an ordinary user.
* No privilege penalty was applied because host-admin-equivalent privilege is not positively established, while complete below-host-admin reachability is also unresolved.
* No race penalty was applied because the documented trigger is deterministic and easily reproducible.
* Controlled reclaim, arbitrary write, precise adjacent-object selection, and demonstrated privilege escalation are not established.

3. Reachability analysis

The trigger requires an AF_XDP socket attached to a virtio_net receive queue followed by growth of that queue through an ethtool ring-resize operation. The resize operation normally involves `CAP_NET_ADMIN` over the target network device. AF_XDP zero-copy setup and XDP program attachment may impose additional BPF, network-device, or memory-lock requirements depending on the kernel and configuration.

The supplied material does not establish whether all required operations can be completed using capabilities obtained in an attacker-created user or network namespace. A namespace-local capability for one stage would not prove that control of the virtio_net device and the complete XDP setup are namespace-scoped. Therefore both host-admin and namespace-scoped reachability remain unknown.

A virtio_net device and AF_XDP support must already exist, but no unusual physical hardware is required. The issue is local control-plane triggered rather than remotely packet-triggered. No race or special timing is necessary.

4. Primitive and severity interpretation

The exact primitive is an attacker-triggered kernel heap OOB write of pointer-sized `struct xdp_buff` values. The old `xsk_buffs` allocation remains sized for the original RX ring while resume processing uses the enlarged virtqueue size.

This is not a UAF, stale-object access, double release, or refcount violation. It is broader than an invalid read or immediate NULL dereference because multiple writes can cross the allocation boundary. The attacker can influence how far the ring grows and therefore the potential overwrite extent. However, the supplied evidence does not show direct control over pointer values, allocator placement, the adjacent victim object, or a useful corrupted field.

The demonstrated primitive supports kernel memory corruption and likely crash or DoS. Privilege escalation is a technically relevant but unproven consequence requiring analysis of allocation type, neighboring objects, write count, and whether the kernel-derived pointer values can produce useful structured corruption.

`PrimitiveClass=CLASS_A` is used because an attacker-triggered heap OOB write with controllable extent is directly established. `ImportantCandidate=YES` and `AutoDowngradeAllowed=NO` follow from this concrete corruption primitive, not from a presumed exploit. The unresolved complete privilege boundary prevents a higher score without additional evidence.

5. One-sentence report phrase

Growing a virtio_net RX ring while AF_XDP is attached can make `virtnet_rx_resume()` write kernel pointers beyond the old `xsk_buffs` allocation, creating a local kernel heap corruption primitive with likely crash impact and unresolved privilege-escalation potential.

6. Manual review recommendation

MANUAL CHECK REQUIRED

Determine the allocator layout, maximum overwrite extent, pointer-value influence, adjacent victim objects, and whether the complete AF_XDP plus ring-resize sequence is reachable below host-admin privilege.

7. Call-site confidence

Call-site confidence: high

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

Patch: virtio_net: Fix resize of the RX ring [ Upstream
Commit: 8344c9233c8f77017174d9e280c5a26034d068b6
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8344c9233c8f77017174d9e280c5a26034d068b6

Changed files:
  drivers/net/virtio_net.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=8344c9233c8f77017174d9e280c5a26034d068b6

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

The original Linux kernel CVE announcement for CVE-2026-90142 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90142

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:L/PR:H/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 7.8

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: unknown
  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).