[CVE-2026-98559][MODERATE 7.0] net/smc: fix UAF on lgr list traversal in smcr_port_err() [ Upstream

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

CVE: CVE-2026-98559
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: net/smc: fix UAF on lgr list traversal in smcr_port_err() [ Upstream
Commit: 34bcf11cd2528ae00bb6d764d808083c66824277
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=34bcf11cd2528ae00bb6d764d808083c66824277
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98559
Analysis date: Sat, 24 Oct 2026 07:52:30 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES

Summary:
A lockless SMC-R link-group traversal can race with group destruction, causing active processing of a freed link group and a likely kernel crash with unresolved post-reuse leverage.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-98559 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98559

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-2026-98559	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-98559 CHECK WITH IMPACT FROM ORIG NN IMPORTANT | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=5 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:A/AC:H/PR:N/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:L/I:L/A:H';BEST CVSS score: '7.5';DESCR 'smcr_port_err traverses the global SMC R link group list lacking smc_lgr_list.lock and can race with smc_lgr_terminate_sched freeing the current link group. The resulting UAF can dereference freed pnet ID, link type, and embedded link state and may schedule link down handling through memory that has already been released or reused. A local AF_SMC user can contribute connection and link group churn, but successful triggering also requires a concurrent port error or stale GID event, so AC:H is appropriate. For the CVSS the PR:N value in the paranoid vector reflects a possible adjacent SMC R peer that can influence link group termination lacking a local user context, although reliable remote control of the overlapping port or GID event is not established. Impact is at least kernel crash and host denial of service. Reuse of the freed link group may also create confidentiality or integrity impact, so the confirmed UAF requires manual analysis. Automated impact decision path. The original SimpleNet classifier selected IMPORTANT. The primary LLM estimated paranoid CVSS 7.5 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 KP and FD specialist checks stage IMPORTANT to MODERATE_KPANIC because FD false positive review allowed a downgrade. 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 produced a review artifact and its decision was processed by the applicable downgrade and preservation rules. Exact triggered rule markers were DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFDH. The independent weaker Aegis shadow evaluated CVSS 2.5 and ActionableScore 5 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	LOCK UAF LINUS KPANIC  DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFDH	-	-	checked

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ACTIONABLESCORE ANALYSIS
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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; the Real UAF floor 4 confirms rather than changes the score.
* Raw paranoid score: 5.
* Paranoid score: 5; no cap or floor adjustment.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::

2. Signal breakdown

* +2 Real UAF: unlocked traversal can dereference an `smc_link_group` concurrently freed by `smc_lgr_terminate_sched()`.
* +1 reliable kernel crash/strong DoS: dereferencing or processing a freed link group plausibly causes a host kernel fault.
* +1 structured stale-object leverage: the stale path reads `pnet_id` and embedded link state and may pass an embedded link to `smcr_link_down_cond_sched()`, extending use beyond a single shallow fault.
* Paranoid +1 attacker-influenced lifetime churn: AF_SMC users or peers can plausibly contribute repeated link-group creation/termination, though control of the overlapping port-error/GID event is incomplete.

Not awarded: remote reachability, controlled reclaim, attacker-shaped replacement contents, arbitrary write, callback control, confidentiality, integrity, or LPE. The crash is counted only once. This is not a repeated-release/refcount case, so no repeated-release signal or floor 5 applies.

3. Reachability analysis

A local AF_SMC user or adjacent SMC-R peer can influence connection and link-group churn, but the complete trigger additionally requires overlap with a port error or stale-GID event. The evidence does not establish that either actor can reliably cause that event, nor which privilege or namespace governs the complete sequence. No hard-race penalty is applied because the race is described but not shown to be unusually narrow or one-shot. RDMA-capable SMC-R infrastructure is required, but the evidence does not justify a rare-hardware penalty.

4. Primitive and severity reading

This is an active structured-object UAF, not fixed stale storage and not merely cleanup-time dereferencing. The stale object is consumed during list traversal and link-down scheduling. A crash is supported; useful reuse, directed corruption, disclosure, and privilege escalation remain unproven. CLASS_B and ImportantCandidate=YES reflect unresolved leverage from continued processing of freed structured state. Auto-downgrade is disallowed because reducing it to crash-only would discard that concrete active-object consumption.

There is no authorization decision or B4-PENDING issue.

5. One-sentence report phrase

A lockless SMC-R link-group traversal can race with group destruction, causing active processing of a freed link group and a likely kernel crash with unresolved post-reuse leverage.

6. Manual review advice

MANUAL CHECK REQUIRED

Review complete trigger privileges, control over the port/GID event, and whether slab reuse can influence the embedded link passed to later scheduling.

7. Call-site confidence

Call-site confidence: medium

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

Patch: net/smc: fix UAF on lgr list traversal in smcr_port_err() [ Upstream
Commit: 34bcf11cd2528ae00bb6d764d808083c66824277
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=34bcf11cd2528ae00bb6d764d808083c66824277

Changed files:
  net/smc/smc_core.c
  net/smc/smc_ib.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=34bcf11cd2528ae00bb6d764d808083c66824277

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

The original Linux kernel CVE announcement for CVE-2026-98559 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98559

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:L/I:L/A:H
  The Best / paranoid CVSS vector: AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 7.5

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: 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).