[CVE-2026-98895][MODERATE 7.0] net/mlx5: HWS, Handle destroying table that has a miss table [ Upstream

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

CVE: CVE-2026-98895
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: net/mlx5: HWS, Handle destroying table that has a miss table [ Upstream
Commit: 16b81428f7b5f253ab30a998bc4f4ecd1c8823f8
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=16b81428f7b5f253ab30a998bc4f4ecd1c8823f8
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98895
Analysis date: Mon, 26 Oct 2026 21:53:22 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES

Summary:
Destroying an mlx5 HWS table without unlinking its embedded default-miss node leaves freed structured state reachable by later list traversal or update, enabling a crash and possible list corruption.

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

The original Linux kernel CVE announcement for CVE-2026-98895 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98895

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-2026-98895	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-98895 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=1 LEGACY=MODERATE_KPANIC RESULT=SAME (final reconciliation agrees; DECISION: both MODERATE_KPANIC)	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';*CWE-416;*CWE-672;*CWE-664;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.8';DESCR 'Destroying an mlx5 HWS table that remains linked through default_miss.next leaves an embedded list node in the miss table after the table object can be freed. A later traversal or update of that miss table can access freed storage and may cause a kernel crash or linked list corruption. The trigger is local and requires control of privileged mlx5 HWS flow steering configuration. For the CVSS the PR:L value in the paranoid vector reflects a delegated network or RDMA service account that can create, link, and destroy HWS tables without full host administration. Direct remote packet traffic alone is not shown to reach the faulty lifetime sequence. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. The primary LLM estimated paranoid CVSS 5.8 and the production ActionableScore returned 5 with recommendation Actionable Moderate / Strong Important candidate requiring manual review. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage MODERATE_KPANIC to IMPORTANT because the CVSS score, vector or bug class threshold rule was applied. KP and FD specialist checks stage IMPORTANT to MODERATE_KPANIC because KP specialist did not establish a qualifying panic. The legacy KP specialist produced a review artifact and its decision was processed by the applicable KP rules. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were INCREASED_TO_HIGH_BASED_ON_GUESSCVSS and DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFKP. The independent weaker Aegis shadow evaluated CVSS 3.6 and ActionableScore 1 with primitive class CLASS_B and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is MODERATE_KPANIC.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5)	MAYBE	REMOTE INIT SIMPLEFIX NETWORK KPANIC  KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFKP	-	-	checked

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

ActionableScore=5
ActionableScoreLower=4
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw base score: 4.
* Conservative score: 4; no floor or cap applied.
* Raw paranoid score: 5.
* Paranoid score: 5; no floor or cap applied.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::

2. Signal breakdown

* +2 real UAF/lifetime violation: destruction leaves `default_miss.next` linked into `miss_tbl`; freeing `tbl` leaves an embedded list node pointing into expired storage.
* +1 reliable crash/strong DoS: later traversal or modification of that list can dereference freed storage and fault.
* +1 attacker-influenced lifetime sequence: an actor controlling HWS table configuration can create the miss relationship and destroy the linked table.
* Paranoid +1 structured stale-object leverage: a later list update may consume stale `next`/`prev` links and perform list writes, producing linked-list corruption rather than only a read fault.
* No privilege penalty: host-admin-equivalent privilege is not positively established.
* No arbitrary write, controlled reclaim, callback control, disclosure, LPE, or C/I impact is shown.
* No repeated release/refcount signal exists. This is stale list membership, not a second put/free.
* No extra Availability point: the same possible kernel crash is already counted.

3. Reachability analysis

The trigger is local and requires control of mlx5 HWS flow-steering configuration. The evidence supports creation, linking, and destruction as the relevant sequence, but does not establish whether the complete operation requires host administration or can be performed by a delegated network/RDMA service. The governing capability and namespace scope are not shown, so both remain unknown. Direct packet traffic is not sufficient. mlx5 HWS-capable device/configuration is required, but the evidence does not justify a rare-hardware penalty. No hard race is shown; this is an ordered lifetime error.

4. Primitive and severity reading

This is an active structured-object UAF: a freed table’s embedded list node remains visible through another live table and can later be traversed or updated. It is broader than a fixed stale buffer, but the supplied patch does not show controlled reclamation or a directed target, so it remains CLASS_B rather than CLASS_A.

The shown effects are stale list access, plausible kernel crash, and possible list corruption. Exploitation beyond that is unresolved. The privileged HWS consumer plus a credible but unconfirmed delegated-interface boundary makes this an active-state trust-boundary candidate requiring review. Consequently, ImportantCandidate is YES and automatic downgrade is unsafe, without claiming proven Important severity.

5. One-sentence report phrase

Destroying an mlx5 HWS table without unlinking its embedded default-miss node leaves freed structured state reachable by later list traversal or update, enabling a crash and possible list corruption.

6. Manual review advice

MANUAL CHECK REQUIRED

Confirm the later list consumers, whether they perform writes through stale links, and whether delegated RDMA/network credentials can complete the full trigger below host administration.

7. Call-site confidence

Call-site confidence: medium

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

Patch: net/mlx5: HWS, Handle destroying table that has a miss table [ Upstream
Commit: 16b81428f7b5f253ab30a998bc4f4ecd1c8823f8
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=16b81428f7b5f253ab30a998bc4f4ecd1c8823f8

Changed files:
  drivers/net/ethernet/mellanox/mlx5/core/steering/hws/mlx5hws_table.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=16b81428f7b5f253ab30a998bc4f4ecd1c8823f8

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

The original Linux kernel CVE announcement for CVE-2026-98895 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98895

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:H/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:L/I:L/A:H
  The Best / paranoid CVSS score: 5.8

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: 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).