[CVE-2026-98557][LOW] gve: DQO: fix header length used by gve_can_send_tso() for UDP GSO [ Upstream

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

CVE: CVE-2026-98557
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: gve: DQO: fix header length used by gve_can_send_tso() for UDP GSO [ Upstream
Commit: feab3880a72b43913d332c06b75bb80526fa47ba
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=feab3880a72b43913d332c06b75bb80526fa47ba
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98557
Analysis date: Sat, 24 Oct 2026 08:28:46 -0400
ActionableScore: 1
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
Incorrect UDP GSO header accounting can exceed the GVE DQO per-segment descriptor limit and disrupt transmission, without a shown kernel-memory corruption or authorization primitive.

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

The original Linux kernel CVE announcement for CVE-2026-98557 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98557

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: LOW
Manual review required: NO

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
======================================================================

CVE-2026-98557	LOW	https://www.kernelcve.org/list/?q=CVE-2026-98557 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT LOW AEGIS_AS=1 LEGACY=LOW RESULT=SAME (final reconciliation agrees; DECISION: both LOW)	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';CWE-682;*CWE-20;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'gve_can_send_tso used a TCP derived header length for SKB_GSO_UDP_L4 packets. It therefore interpreted a UDP payload byte as TCP doff and could overestimate or underestimate how many data descriptors each hardware segment requires. Underestimation can hand the device a segment spanning more than GVE_TX_MAX_DATA_DESCS buffers, while overestimation only disables hardware GSO and falls back to software segmentation. For the CVSS the PR:L value reflects that reliable triggering normally requires a local process able to generate crafted UDP GSO traffic. No OOB access, UAF, information leak, or memory write primitive is shown. The supported impact is packet transmission disruption, with device or TX queue failure remaining a grounded worst case rather than a proven kernel crash. Direct remote reachability from ordinary received UDP traffic is not established. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. The primary LLM estimated paranoid CVSS 5.5 and the production ActionableScore returned 1 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage MODERATE_KPANIC to MODERATE because the CVSS score, vector or bug class threshold rule was applied. ActionableScore thresholds stage MODERATE to LOW because the ActionableScore threshold rule was applied. final reconciliation stage LOW to LOW because KP specialist did not establish a qualifying panic. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH and DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 and KPANIC_UNSUPPORTED_REMOVED. The independent weaker Aegis shadow evaluated CVSS 3.3 and ActionableScore 1 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was LOW. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is LOW.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1)	MAYBE	REMOTE NETWORK SKB HARDWARE PACKET DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 KPANIC_UNSUPPORTED_REMOVED	-	-	checked

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

ActionableScore=1
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
RequiresHostUID0=NO
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw base score: 1.
* Conservative score: 1; no floor or cap applied.
* Raw paranoid score: 1.
* Paranoid score: 1; no additional technically supported primitive.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

* +1 Availability impact plausible: the incorrect UDP header length can underestimate descriptor use and submit a segment spanning more than `GVE_TX_MAX_DATA_DESCS`, plausibly disrupting transmission or the TX queue.
* No reliable kernel-crash point: neither the patch nor commit establishes a panic or host-wide fatal fault.
* No corruption point: the only identified invalid read is a UDP payload byte interpreted as TCP `doff`; it remains within packet data, and no heap/slab OOB write or kernel-memory overwrite is shown.
* No B5-R: there is no retry-accumulated index, retry-controlled sequence, OOB write, or later consumption of corrupted heap state.
* No remote bonus: ordinary received UDP traffic does not establish control of the locally transmitted GSO skb.
* No C/I, arbitrary write, UAF, controlled reclaim, or security-boundary primitive is shown.

3. Reachability analysis

An ordinary local process can plausibly generate UDP GSO traffic routed through a GVE DQO interface without host-administrator powers, supporting `HostAdminRequired=NO` and `RequiresHostUID0=NO`. The evidence does not establish that the complete path depends on namespace-scoped capabilities, so that field remains unknown. A GVE device and DQO UDP-GSO transmit path are required, but this is a deployment prerequisite rather than rare physical attacker access. No race, retry sequence, prior privileged policy setup, or authorization bypass is involved.

4. Primitive and severity reading

The defect is an arithmetic/validation mismatch: TCP header semantics are applied to a UDP GSO packet, causing inaccurate per-segment descriptor counting. The resulting device submission can exceed the driver's intended descriptor-per-segment limit, but no host-memory OOB access, descriptor-array overwrite, stale lifetime use, or active structured-state corruption is demonstrated. This is CLASS_C invalid-state/availability behavior. Stronger outcomes such as device reset or kernel crash remain unproven. There is no Important-preserving primitive, so automatic Moderate handling is allowed.

5. One-sentence report phrase

Incorrect UDP GSO header accounting can exceed the GVE DQO per-segment descriptor limit and disrupt transmission, without a shown kernel-memory corruption or authorization primitive.

6. Manual review advice

NO MANUAL CHECK NEEDED

The patch supports a constrained descriptor-accounting and availability issue, not an unresolved corruption or trust-boundary primitive.

7. Call-site confidence

Call-site confidence: medium

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

Patch: gve: DQO: fix header length used by gve_can_send_tso() for UDP GSO [ Upstream
Commit: feab3880a72b43913d332c06b75bb80526fa47ba
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=feab3880a72b43913d332c06b75bb80526fa47ba

Changed files:
  drivers/net/ethernet/google/gve/gve_tx_dqo.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=feab3880a72b43913d332c06b75bb80526fa47ba

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

The original Linux kernel CVE announcement for CVE-2026-98557 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98557

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:L/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 5.5

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: 1

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: LOW
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): LOW

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).