* [CVE-2026-98580][MODERATE 7.0] nfc: llcp: Fix race condition in accept_queue lifecycle [ Upstream
@ 2026-10-24 14:34 21% AL-KERNEL
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From: AL-KERNEL @ 2026-10-24 14:34 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-98580
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: nfc: llcp: Fix race condition in accept_queue lifecycle [ Upstream
Commit: 54adcabb0f1deef1bdae5fc64779ed6d442721c9
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=54adcabb0f1deef1bdae5fc64779ed6d442721c9
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98580
Analysis date: Sat, 24 Oct 2026 10:34:08 -0400
ActionableScore: 5
ActionableScore lower bound: unknown
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES
Summary:
A synchronization race between LLCP accept and socket teardown can unlink and `sock_put()` the same child twice, causing a real socket UAF or NULL-pointer kernel crash.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98580 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98580
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.
======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================
CVE-2026-98580 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-98580 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=4 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:H/I:H/A:H';CWE-362;*CWE-416;**CWE-476;CWE-667;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'This is a race and kernel object lifetime flaw in the NFC LLCP accept queue. nfc_llcp_socket_release and nfc_llcp_accept_dequeue can concurrently unlink and release the same child socket because bh_lock_sock does not synchronize with process context lock_sock. The resulting primitive is a use after free with an additional possible NULL pointer dereference through child parent. For the CVSS the PR:L value is selected because reliable triggering requires a local process able to create and operate NFC LLCP sockets and coordinate accept with listener or device teardown. AC:H reflects the required race window. Impact is at least a local denial of service through a kernel crash and may include confidentiality or integrity impact if the freed socket object is reused. A remote NFC peer may influence connection creation and timing but cannot independently perform the required local accept and release operations. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. The primary LLM estimated paranoid CVSS 7 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 MODERATE_KPANIC because the CVSS score, vector or bug class threshold rule was applied. 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 LOWERED_FROM_HIGH_BASED_ON_NULLPTR. The independent weaker Aegis shadow evaluated CVSS unavailable and ActionableScore 4 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 DANGER NULLPTR INIT NOMEMCHK RACE UAF HARDWARE LINUS KPANIC KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS KPANIC LOWERED_FROM_HIGH_BASED_ON_NULLPTR - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=5
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: 3.
* Conservative score: 5. REAL UAF FLOOR 5 applies because the exact child can receive a second non-idempotent `sock_put()` after the first concurrent unlink/release may end its lifetime.
* Raw paranoid score: 4.
* Paranoid score: 5. The extra point reflects the specifically evidenced write-like refcount mutation through potentially post-lifetime storage; the same floor produces no score difference.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::
2. Signal breakdown
* +2 Real UAF: release and accept paths concurrently unlink and release the same child socket.
* +1 Concrete repeated release/refcount: old `nfc_llcp_accept_unlink()` unconditionally executes `sock_put(sk)`; both racing paths can invoke it on the exact child.
* +1 Reliable kernel crash: the commit supports UAF and `child->parent` NULL dereference.
* -1 Hard race: concurrent accept and teardown must hit the synchronization window; the supplied evidence characterizes this as AC:H.
* Paranoid +1: the second `sock_put()` can mutate refcount/lifetime state after the first release may have ended the object lifetime.
* FLOOR 5 applied: first release can end lifetime, the same reference survives, and the second lifetime mutation is specific and non-idempotent.
Controlled reclaim, attacker-shaped replacement contents, arbitrary write, disclosure, LPE, and C/I impact are not shown. No extra availability point is awarded for the same crash. Structured-object leverage and Weak LPE are not separately counted because the relevant evidence is already the repeated refcount mutation.
3. Reachability analysis
A local process can operate LLCP sockets and influence accept/listener-close timing, but the patch does not fully establish whether the vulnerable `nfc_llcp_socket_release()` sequence requires device teardown or privileged NFC configuration. Thus below-host-admin complete reachability and namespace capability scope remain unknown. An NFC LLCP-capable device and registered local state appear necessary. Repeated attempts are plausible, but the race window remains timing-sensitive.
4. Primitive and severity reading
This is an active socket lifetime violation, not fixed stale storage. It is stronger than an ordinary cleanup dereference: two paths can perform unlink plus `sock_put()` on the same child, making the second operation a lifetime/refcount mutation through a potentially dangling object. That supports CLASS_B, not CLASS_A: no controlled reclaim or directed corruption is shown.
Crash/UAF is demonstrated; useful post-reuse exploitation remains unresolved. The concrete repeated lifetime mutation makes this an Important candidate requiring review and prevents automatic downgrade, without proving Important severity or privilege escalation. B4 authorization-state rules do not apply.
5. One-sentence report phrase
A synchronization race between LLCP accept and socket teardown can unlink and `sock_put()` the same child twice, causing a real socket UAF or NULL-pointer kernel crash.
6. Manual review advice
MANUAL CHECK REQUIRED
The second refcount mutation through a possibly freed socket leaves material post-lifetime corruption leverage unresolved.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: nfc: llcp: Fix race condition in accept_queue lifecycle [ Upstream
Commit: 54adcabb0f1deef1bdae5fc64779ed6d442721c9
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=54adcabb0f1deef1bdae5fc64779ed6d442721c9
Changed files:
net/nfc/llcp.h
net/nfc/llcp_core.c
net/nfc/llcp_sock.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=54adcabb0f1deef1bdae5fc64779ed6d442721c9
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98580 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98580
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: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: 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 [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
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