* [CVE-2026-98906][MODERATE REGULAR] net: lan966x: restore RX state on reload failure [ Upstream
@ 2026-10-27 4:31 21% AL-KERNEL
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From: AL-KERNEL @ 2026-10-27 4:31 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-98906
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: net: lan966x: restore RX state on reload failure [ Upstream
Commit: 3883898ddc26308497dbba8068951ab5eddbd111
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3883898ddc26308497dbba8068951ab5eddbd111
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98906
Analysis date: Tue, 27 Oct 2026 00:31:39 -0400
ActionableScore: 4
ActionableScore lower bound: unknown
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES
Summary:
Failed LAN966x MTU reload can restart RX with stale page-pool registration and mismatched XDP frame geometry, creating an active lifetime and bounds-corruption candidate.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98906 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98906
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 REGULAR
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-2026-98906 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-98906 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=0 LEGACY=MODERATE RESULT=DIFF (final Legacy and Aegis differ; FINAL: MODERATE, Aegis: 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:H/I:H/A:H';*CWE-672;*CWE-787;CWE-755;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'lan966x_fdma_reload can restart RX with old pages and FDMA resources but new page_order and max_mtu values after an allocation failure. The oversized frame geometry passed to xdp_init_buff can let XDP treat memory beyond the restored page as valid frame space, while the XDP RXQ can retain a registration for a newly destroyed page pool. An XDP operation such as tail expansion could then cause an out of bounds write, and later page handling may encounter a stale resource reference. These are plausible kernel memory safety paths, although the available diff does not prove a controlled write or successful privilege escalation. Base C:L and I:L reflect the limited but concrete memory corruption concern, while A:H reflects a plausible kernel crash. For the CVSS the PR:H base value reflects that reliable setup normally requires CAP_NET_ADMIN to change the MTU and an allocation failure. For the CVSS the PR:L paranoid value covers delegated network administration available to a container or service account. The issue is not directly remote because packets only exercise the inconsistent state after the locally initiated failed reload. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. The primary LLM estimated paranoid CVSS 7 and the production ActionableScore returned 4 with recommendation Actionable Moderate / Strong Important candidate requiring manual review. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were KP and FD specialist checks stage MODERATE_KPANIC to MODERATE 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 DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP and V41_INHERITED_KPANIC_PROMOTION_BLOCKED and MANUAL_REVIEW_REQUIRED. The independent weaker Aegis shadow evaluated CVSS 2.1 and ActionableScore 0 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. The models disagreed but the aggregation rules retained the production result. The final reported impact is MODERATE.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 4) MAYBE REMOTE INIT NETWORK LINUS DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP V41_INHERITED_KPANIC_PROMOTION_BLOCKED MANUAL_REVIEW_REQUIRED - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=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 changed the score.
* Raw paranoid score: 4.
* Paranoid score: 4; no additional primitive is sufficiently proven.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::
2. Signal breakdown
* +2 real lifetime violation: the failed allocation destroys the newly registered page pool, while each port's active XDP RXQ can retain that pool registration and RX is restarted.
* +1 weak/indirect corruption candidate: restored old pages can be advertised through `xdp_init_buff()` using the failed configuration's larger `page_order` and frame geometry.
* +1 plausible kernel crash/strong DoS: subsequent XDP or page-pool processing can consume invalid bounds or stale allocator state.
* No privilege penalty: host-admin-equivalent privilege is not positively established.
* No OOB-write bonus: the patch supports oversized frame geometry, but does not show an actual XDP tail expansion or another confirmed write beyond the page.
* No controlled reclaim, arbitrary write, disclosure, C/I impact, or LPE is shown.
* B5-R is not established: there is no retry-accumulated index/offset and no confirmed heap OOB write.
* No extra availability point; it would duplicate the same prospective crash.
3. Reachability analysis
The inconsistent state follows a locally initiated MTU reload plus allocation failure, after which packet reception exercises the state. Changing MTU ordinarily involves network-management authority, but the evidence does not establish whether the complete operation requires host/init-namespace administration, works with delegated `CAP_NET_ADMIN`, or is fully namespace-scoped. XDP setup and the relevant LAN966x device ownership are likewise unresolved. Allocation failure is a trigger condition, but no narrow race is shown, so no timing penalty applies.
4. Primitive and severity reading
The primary primitive is active structured-state lifetime corruption: an XDP RXQ may reference a destroyed page pool while restarted RX continues to use it. This is an implied active-object UAF rather than fixed stale storage. Separately, stale page allocation combined with new frame geometry creates a bounds mismatch consumed by XDP initialization.
A concrete OOB write is plausible but not demonstrated, so this remains CLASS_B rather than CLASS_A. The write geometry, privileged RX/XDP consumers, and unresolved delegated-network boundary form a specific unknown cross-boundary corruption chain; therefore ImportantCandidate is retained and automatic downgrade is disallowed.
5. One-sentence report phrase
Failed LAN966x MTU reload can restart RX with stale page-pool registration and mismatched XDP frame geometry, creating an active lifetime and bounds-corruption candidate.
6. Manual review advice
MANUAL CHECK REQUIRED
Confirm the XDP/page-pool consumer path, whether any adjustment writes beyond the restored page, and the exact capability and namespace boundary for the full trigger.
7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: net: lan966x: restore RX state on reload failure [ Upstream
Commit: 3883898ddc26308497dbba8068951ab5eddbd111
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3883898ddc26308497dbba8068951ab5eddbd111
Changed files:
drivers/net/ethernet/microchip/lan966x/lan966x_fdma.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=3883898ddc26308497dbba8068951ab5eddbd111
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98906 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98906
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:L/I:L/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: unknown
Paranoid ActionableScore: 4
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: NO
Published priority for this report (same as in Subject): MODERATE REGULAR
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 [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
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