* [CVE-2026-98578][IMPORTANT] nfc: st21nfca: validate ISO15693 inventory length [ Upstream
@ 2026-10-24 10:05 21% AL-KERNEL
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From: AL-KERNEL @ 2026-10-24 10:05 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-98578
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: NO
Patch: nfc: st21nfca: validate ISO15693 inventory length [ Upstream
Commit: e47b2a350bb0ff123434ec5484c6dc3333b0727c
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e47b2a350bb0ff123434ec5484c6dc3333b0727c
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98578
Analysis date: Sat, 24 Oct 2026 06:05:33 -0400
ActionableScore: 5
ActionableScore lower bound: unknown
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES
Summary:
A malformed ISO15693 inventory response can underflow the UID-copy length and trigger an oversized kernel heap write, with crash proven plausible but stronger exploitation unresolved.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98578 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98578
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: IMPORTANT
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-2026-98578 IMPORTANT https://www.kernelcve.org/list/?q=CVE-2026-98578 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=2 LEGACY=IMPORTANT RESULT=DIFF INDEPENDENT_LEGACY=IMPORTANT INDEPENDENT_RESULT=DIFF TEMP_KPANIC_MERGE=IMPORTANT_WINS_DISAGREEMENT PRE_MERGE_LEGACY=IMPORTANT (final Legacy and Aegis differ; FINAL: IMPORTANT, Aegis: MODERATE_KPANIC) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H';*CWE-20;CWE-125;CWE-191;*CWE-787;Other CVSS 'AV:A/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:H';BEST CVSS score: '8.8';DESCR 'The ISO15693 inventory parser can accept a response with only one byte left after prefix removal and then read the second byte as the DSFID. The same short length can make the UID copy length underflow when it is calculated as the remaining length minus two, creating an out of bounds copy that can crash the kernel and may corrupt memory. A malicious ISO15693 tag within NFC range can provide the malformed response while the reader performs an inventory operation. For the CVSS the PR:N value is used because the attacker needs no operating system account or local privileges. The base UI:R value assumes that a user or application initiates scanning, while automatic reader polling supports UI:N in the paranoid vector. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 8.8 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 LOW to IMPORTANT because the CVSS score, vector or bug class threshold rule was applied. KP and FD specialist checks stage IMPORTANT to IMPORTANT because a specific evidence based protection or manual review veto was applied. final reconciliation stage IMPORTANT to IMPORTANT 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 produced a review artifact and its decision was processed by the applicable downgrade and preservation rules. Exact triggered rule markers were INCREASED_TO_HIGH_BASED_ON_GUESSCVSS8.5PLUS and V42_LEGACY_CLASSA_FD_VETO and MANUAL_REVIEW_REQUIRED and TEMP_KPANIC_MERGE_IMPORTANT_WINS and KPANIC_UNSUPPORTED_REMOVED. The independent weaker Aegis shadow evaluated CVSS 0.0 and ActionableScore 2 with primitive class CLASS_C and manual review REQUIRED. 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 IMPORTANT.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5) MAYBE SIMPLEFIX SKB LINUS INCREASED_TO_HIGH_BASED_ON_GUESSCVSS8.5PLUS V42_LEGACY_CLASSA_FD_VETO MANUAL_REVIEW_REQUIRED TEMP_KPANIC_MERGE_IMPORTANT_WINS KPANIC_UNSUPPORTED_REMOVED - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=5
PrimitiveClass=CLASS_A
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO
RequiresHostUID0=NO
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO
1. ActionableScore
* Raw base score: 4.
* Conservative score: 5. Manual-review safety floor applied: 4 -> 5 for a concrete attacker-influenced heap OOB write.
* Raw paranoid score: 4.
* Paranoid score: 5. Same floor; no additional speculative effects scored.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::
2. Signal breakdown
* +2 — Strong corruption primitive: accepting `len == 1` after prefix removal makes the UID-copy length `len - 2` underflow, causing an oversized write beyond the destination UID storage.
* +1 — Firmware/device-mediated external influence: a nearby malicious ISO15693 tag can supply the malformed inventory response.
* +1 — Reliable kernel crash/strong DoS is plausible from the oversized copy and resulting invalid memory access.
* No retry/re-entry accumulation exists; NEW52 B5-R does not apply.
* No controlled target, arbitrary payload, named adjacent victim, disclosure, or LPE is shown.
* No extra integrity or availability point: kernel memory corruption and its likely crash are already counted.
* No remote-network bonus: NFC proximity is not ordinary remote reachability.
* No physical/rare-hardware penalty: NFC hardware is required, but the evidence does not establish rare hardware or physical contact/access.
3. Reachability analysis
The supported attacker is a nearby malicious NFC tag, requiring an NFC reader to perform inventory scanning. The supplied evidence describes no OS account, host UID 0, capability, namespace privilege, or host-administrator requirement. User/application initiation may be required; automatic polling is possible but not proven as the universal path. No timing race or retry sequence is involved.
4. Primitive and severity reading
The primitive is an attacker-triggered heap/slab OOB write caused by unsigned copy-length underflow, not a UAF or read-only overrun. The destination is fixed and arbitrary target selection is not shown, but the copy is not harmlessly bounded. CLASS_A is appropriate for the concrete attacker-influenced OOB write. ImportantCandidate is retained because exploit leverage beyond crash is unresolved; AutoDowngradeAllowed is NO. B3-PENDING and B4-PENDING are inapplicable.
5. One-sentence report phrase
A malformed ISO15693 inventory response can underflow the UID-copy length and trigger an oversized kernel heap write, with crash proven plausible but stronger exploitation unresolved.
6. Manual review advice
MANUAL CHECK REQUIRED
Concrete externally influenced kernel OOB write requires Important-versus-Moderate exploit-leverage review.
7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: nfc: st21nfca: validate ISO15693 inventory length [ Upstream
Commit: e47b2a350bb0ff123434ec5484c6dc3333b0727c
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e47b2a350bb0ff123434ec5484c6dc3333b0727c
Changed files:
drivers/nfc/st21nfca/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=e47b2a350bb0ff123434ec5484c6dc3333b0727c
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98578 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98578
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:A/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:H
The Best / paranoid CVSS vector: AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
The Best / paranoid CVSS score: 8.8
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: unknown
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: IMPORTANT
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): IMPORTANT
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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