[CVE-2026-98456][IMPORTANT] Bluetooth: mgmt: fix race in read_unconf_index_list()

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

CVE: CVE-2026-98456
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: NO
Patch: Bluetooth: mgmt: fix race in read_unconf_index_list()
Commit: 524e0450dd9a396f99a81b045219b0e2ea0dab57
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=524e0450dd9a396f99a81b045219b0e2ea0dab57
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98456
Analysis date: Sat, 24 Oct 2026 03:21:45 -0400
ActionableScore: 5
ActionableScore lower bound: unknown
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES

Summary:
A Bluetooth management count/fill race can write controller indexes beyond a heap response buffer, with crash plausible but useful adjacent-object corruption and complete low-privilege reachability unresolved.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-98456 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98456

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.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-98456	IMPORTANT	https://www.kernelcve.org/list/?q=CVE-2026-98456 CHECK WITH IMPACT FROM ORIG NN IMPORTANT | 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:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';CWE-362;*CWE-787;CWE-122;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'A race in Bluetooth management read_unconf_index_list can cause the response buffer to be allocated for fewer controllers than become eligible during the fill pass. hci_dev_list_lock keeps list membership stable but does not serialize HCI_UNCONFIGURED and HCI_SETUP flag transitions. The concrete primitive is a heap out of bounds write of one or more __le16 controller index values beyond rp index. Triggering requires local access to the Bluetooth management control socket and a concurrent asynchronous controller setup transition, so AC:H reflects the race window. For the CVSS the PR:L value reflects that an attacker needs an authorized local process or delegated Bluetooth management access, while full unrestricted root control is not necessarily required in practical service or container deployments. The issue is not directly reachable through ordinary remote Bluetooth packets. Availability impact can include a kernel crash, while confidentiality and integrity impact depend on whether the constrained overwrite can corrupt a useful adjacent heap object. Automated impact decision path. The original SimpleNet classifier selected IMPORTANT. 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 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 V59_LEGACY_CLASSA_KP_VETO and MANUAL_REVIEW_REQUIRED 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 2.4 and ActionableScore 2 with primitive class CLASS_B 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	REMOTE WRITE OOB SIMPLEFIX RACE NETWORK HARDWARE LINUS V59_LEGACY_CLASSA_KP_VETO MANUAL_REVIEW_REQUIRED V42_LEGACY_CLASSA_FD_VETO MANUAL_REVIEW_REQUIRED TEMP_KPANIC_MERGE_IMPORTANT_WINS KPANIC_UNSUPPORTED_REMOVED	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=5
PrimitiveClass=CLASS_A
RealUAF=NO
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: 2.
* Conservative score: 5. Manual-review safety floor applied: 2 -> 5 for a confirmed attacker-triggerable heap out-of-bounds write.
* Raw paranoid score: 2.
* Paranoid score: 5. No additional speculative leverage awarded.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::

2. Signal breakdown

* +2 Strong corruption primitive: the first pass allocates for currently unconfigured controllers, while the unlocked flags can change before the fill pass, causing one or more `__le16` writes beyond `rp->index[]`.
* +1 Reliable kernel crash/strong DoS plausible from heap corruption; no separate availability point.
* -1 Hard race: exploitation requires an asynchronous setup flag transition between counting and filling; the supplied summary explicitly characterizes this as AC:H.
* No privilege penalty: host-admin-equivalent privilege is not positively established.
* No confidentiality, integrity, arbitrary-write, controlled-target, controlled-reclaim, or LPE bonus. Written values are controller indexes and the adjacent victim is unidentified.
* B5-R is not established: there is no retry-accumulated index or missing retry reset, and no later consumption of specifically identified corrupted structured state is shown.
* B4 does not apply because no authorization decision changes from DENY to ALLOW.

3. Reachability analysis

A local process must invoke the Bluetooth management command while controller setup changes `HCI_UNCONFIGURED`/`HCI_SETUP`. The supplied evidence grounds local management-socket access but does not establish whether the complete trigger requires host CAP_NET_ADMIN, delegated service access, or a namespace-scoped capability. It also does not prove that the attacker can initiate the setup transition rather than merely race an externally occurring transition. No remote Bluetooth-packet path is shown. Bluetooth hardware is required, but it is not shown to be rare enough for a hardware penalty.

4. Primitive and severity reading

The exact primitive is a confirmed heap OOB write of one or more two-byte controller indexes caused by a count/fill TOCTOU. This is not a UAF, fixed stale-storage issue, authorization bypass, or retry-accumulation flaw. Heap corruption and possible crash are supported; useful adjacent-object corruption and later structured-state consumption remain unproven. It is CLASS_A because an attacker-invocable operation can produce a real heap OOB write, but the constrained payload and unresolved race control prevent stronger impact claims. ImportantCandidate is YES and auto-downgrade is disallowed because the concrete write primitive requires exploit-leverage review.

5. One-sentence report phrase

A Bluetooth management count/fill race can write controller indexes beyond a heap response buffer, with crash plausible but useful adjacent-object corruption and complete low-privilege reachability unresolved.

6. Manual review advice

MANUAL CHECK REQUIRED

Confirm management-socket privilege scope, attacker control over controller setup transitions, overwrite extent, allocator placement, and whether an adjacent kernel object is subsequently consumed.

7. Call-site confidence

Call-site confidence: medium

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

Patch: Bluetooth: mgmt: fix race in read_unconf_index_list()
Commit: 524e0450dd9a396f99a81b045219b0e2ea0dab57
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=524e0450dd9a396f99a81b045219b0e2ea0dab57

Commit description:

read_unconf_index_list() counts unconfigured controllers before allocating
its response, then checks the device flags again while filling it.

hci_dev_list_lock stabilizes list membership, but it does not serialize the
per-device flags. During asynchronous controller setup, the worker can set
HCI_UNCONFIGURED and clear HCI_SETUP between the two passes. A controller
omitted from the allocation count can then become eligible for the fill
pass, causing an out-of-bounds write to rp->index[].

Allocate space for every device on hci_dev_list. Since list membership
cannot change while hci_dev_list_lock is held, the response remains large
enough regardless of flag transitions. The reported count and response
length still include only eligible unconfigured controllers.

Fixes: 73d1df2 ("Bluetooth: Add support for Read Unconfigured Index List command")
Cc: stable@vger.kernel.org
Signed-off-by: Aldo Ariel Panzardo <qwe.aldo@gmail.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  net/bluetooth/mgmt.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=524e0450dd9a396f99a81b045219b0e2ea0dab57

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

The original Linux kernel CVE announcement for CVE-2026-98456 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98456

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