[CVE-2026-98576][MODERATE REGULAR] nfc: llcp: fix slab-out-of-bounds reads when logging service names [ Upstream

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

CVE: CVE-2026-98576
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: nfc: llcp: fix slab-out-of-bounds reads when logging service names [ Upstream
Commit: 75f7c5a42fa1483f5912279a749417c284ad708f
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=75f7c5a42fa1483f5912279a749417c284ad708f
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98576
Analysis date: Sun, 18 Oct 2026 23:34:53 -0400
ActionableScore: 1
ActionableScore lower bound: 0
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
Non-null-terminated NFC LLCP service names can cause pr_debug to read beyond a slab allocation, potentially exposing adjacent bytes in an enabled kernel debug log, but no write, UAF, privilege escalation, or confirmed remote trigger is established.

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

The original Linux kernel CVE announcement for CVE-2026-98576 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98576

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: 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-2026-98576	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-98576 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=2 LEGACY=MODERATE RESULT=DIFF V39_AEGIS_ONE_STEP_UP=LOW->MODERATE TEMP_DISTANCE_MERGE_SKIP=AEGIS_NO_POSITIVE_SEVERITY_EVIDENCE (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:L/I:N/A:H';CWE-125;CWE-126;CWE-170;*CWE-200;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:L';BEST CVSS score: '5.3';DESCR 'An out of bounds read occurs in the NFC LLCP service name logging paths because non null terminated buffers are passed to pr_debug with the percent s format. The logging code can continue reading beyond the allocated object until a zero byte is encountered, potentially exposing adjacent slab data in the kernel debug log or causing a kernel fault. For the CVSS the PR:L reflects that a local user or process must reach the NFC LLCP or netlink interface and supply the affected string data. AC:H reflects the additional dependency on pr_debug or dynamic debug being active and on a suitable heap layout. The confirmed primitive is an out of bounds read rather than a write, so integrity impact and privilege escalation are not supported. Remote triggering by an NFC peer is not established by this diff and requires caller analysis. Impact is a possible local information disclosure and denial of service, with the paranoid score allowing high availability impact while retaining limited confidentiality impact. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 5.3 and the production ActionableScore returned 1 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were final reconciliation stage LOW to MODERATE because KP specialist did not establish a qualifying panic and the cross model evidence reconciliation rule was applied. 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 KPANIC_UNSUPPORTED_REMOVED and V39_AEGIS_ONE_STEP_UP and MANUAL_REVIEW_REQUIRED. The independent weaker Aegis shadow evaluated CVSS 2.5 and ActionableScore 2 with primitive class CLASS_C and manual review RECOMMENDED. Its independently reconciled impact was MODERATE_KPANIC. Cross model aggregation changed the production result under an enabled evidence gated merge rule. The final reported impact is MODERATE.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1)	MAYBE	READ KASAN OOB SIMPLEFIX LINUS SYZBOT KPANIC_UNSUPPORTED_REMOVED V39_AEGIS_ONE_STEP_UP MANUAL_REVIEW_REQUIRED	-	-	checked

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

ActionableScore=1
ActionableScoreLower=0
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw conservative score: 0.
* Conservative score: 0.
* Raw paranoid score: 1.
* Paranoid score: 1.
* No floor or cap was applied.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

Conservative signals:

* +0 Limited slab out-of-bounds read. `%s` reads beyond a non-null-terminated allocation, but no write, UAF, control-flow effect, or confirmed attacker-visible disclosure is established.
* No negative points. Privilege, namespace scope, and remote reachability are unresolved rather than assumed restrictive.

Paranoid signal:

* +1 Plausible confidentiality impact. When `pr_debug` or dynamic debug is active, bytes following the allocation can be formatted into the kernel log. Actual attacker access to that log is not established.

Not awarded:

* No crash point. KASAN detects the invalid read, but the supplied evidence does not establish a reliable production-kernel panic.
* No integrity point because the operation only reads memory.
* No remote-reachability point because an NFC peer call path is not shown.
* No local-unprivileged point because netlink permissions for the complete trigger are not supplied.
* No B5-R signal because there is no retry-accumulated OOB write.
* No B3-PENDING signal because there is no write to shared backing.
* No active-state or trust-boundary signal because no structured state is modified or consumed.
* No authorization signal because the patch changes logging bounds, not an ALLOW-versus-DENY decision.

3. Reachability analysis

The strings originate from `kmemdup` allocations or netlink attributes, so local process influence is credible, but the supplied context does not establish which credentials are accepted by the complete NFC LLCP operation. Therefore both host-administrator and namespace-scoped privilege requirements remain unknown.

A practical disclosure additionally requires the affected `pr_debug` call to be enabled and the attacker to obtain the resulting kernel log. NFC hardware or an configured LLCP path may also be required. Direct triggering by a remote NFC peer is not established. There is no race or retry requirement.

4. Primitive and severity interpretation

The exact primitive is an unbounded slab read caused by applying `%s` to a buffer that is not guaranteed to contain a terminating NUL. It is neither a lifetime violation nor an active structured-object corruption.

The demonstrated consequence is a KASAN slab-out-of-bounds report. A limited kernel-log disclosure is plausible because the bytes are processed for diagnostic output, but attacker access to that output is unresolved. A kernel fault is possible in principle if scanning reaches inaccessible memory, but it is not sufficiently established to receive a score point.

This is CLASS_C rather than CLASS_B because no write, UAF, stale lifetime operation, authorization bypass, or independently useful corruption primitive exists. ImportantCandidate is NO. AutoDowngradeAllowed is YES because no unresolved Important-preserving primitive is present.

5. One-sentence report phrase

Non-null-terminated NFC LLCP service names can cause pr_debug to read beyond a slab allocation, potentially exposing adjacent bytes in an enabled kernel debug log, but no write, UAF, privilege escalation, or confirmed remote trigger is established.

6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Verify netlink permission checks, remote NFC peer reachability, dynamic-debug configuration, and access to kernel logs before assigning confidentiality or stronger availability impact.

7. Call-site confidence

Call-site confidence: medium

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

Patch: nfc: llcp: fix slab-out-of-bounds reads when logging service names [ Upstream
Commit: 75f7c5a42fa1483f5912279a749417c284ad708f
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=75f7c5a42fa1483f5912279a749417c284ad708f

Changed files:
  net/nfc/llcp_commands.c
  net/nfc/llcp_core.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=75f7c5a42fa1483f5912279a749417c284ad708f

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

The original Linux kernel CVE announcement for CVE-2026-98576 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98576

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:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:H
  The Best / paranoid CVSS score: 5.3

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: 0
  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: 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 alexanjelausa@gmail.com (and both
send reply to CVE record itself too and see "reply" button below for howto reply).