[CVE-2026-98246][MODERATE REGULAR] Bluetooth: hci_sync: Serialize local codec list cleanup

[CVE-2026-98246][MODERATE REGULAR] Bluetooth: hci_sync: Serialize local codec list cleanup

[AL-KERNEL]

CVE: CVE-2026-98246
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: Bluetooth: hci_sync: Serialize local codec list cleanup
Commit: 9f407d52c0d881430d689836d3e7d32aa36f98b5
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9f407d52c0d881430d689836d3e7d32aa36f98b5
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98246
Analysis date: Sun, 11 Oct 2026 02:26:37 -0400
ActionableScore: 4
ActionableScore lower bound: unknown
Actionable bucket: Borderline / manual review recommended
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-98246 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98246

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: YES

A detailed explanation of the methodology and priority rules is included
at the end of this message.

======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-98246	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-98246 CHECK WITH IMPACT FROM ORIG NN IMPORTANT | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=4 LEGACY=MODERATE RESULT=DIFF (independent 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:L/A:H';*CWE-416;CWE-362;CWE-667;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:L';BEST CVSS score: '5.8';DESCR 'A race in the Bluetooth HCI close path allows hci_dev_close_sync to free a local codec entry while sco_sock_getsockopt is still reading it under hdev lock. This creates a confirmed slab use-after-free read of entry id and may return stale kernel heap data or cause unstable behavior if the freed object is concurrently reused. For the CVSS the PR:L reflects that a local process can reach the BT_CODEC query path, although reliably forcing the concurrent HCI device close may require delegated CAP_NET_ADMIN or a naturally occurring device teardown. AC:H reflects the narrow timing window required between list traversal and cleanup. The issue is not directly network reachable because a remote Bluetooth peer cannot invoke the local getsockopt operation. Impact is at least limited confidentiality exposure or local disruption and in the paranoid case may include limited integrity impact and a kernel crash due to the confirmed use-after-free. No UAF write or arbitrary write primitive is established, so full HHH impact is not justified.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 4)	MAYBE	REMOTE READ LEAK UAF NETWORK LINUS  LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS  DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP	-	-	checked

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

ActionableScore=4
PrimitiveClass=CLASS_B
RealUAF=YES
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: 2
* Conservative score: 4
* Raw paranoid score: 2
* Paranoid score: 4
* Applied conservative REAL UAF FLOOR 4: 2 -> 4
* Applied paranoid REAL UAF FLOOR 4: 2 -> 4
* Final recommended bucket: **Borderline / manual review recommended**::

2. Signal breakdown

* +2 Real UAF: `hci_codec_list_clear()` frees a codec entry while `sco_sock_getsockopt()` retains and reads that exact entry.
* +1 Confidentiality plausible: the stale one-byte `entry->id` read occurs in a `getsockopt()` output path and can potentially expose a byte from reused slab storage.
* -1 Hard race: exploitation requires the narrow, effectively one-shot interval between fetching the entry and reading its ID while the HCI device close path frees the list.
* No crash point awarded: KASAN confirms the invalid read, but the supplied evidence does not establish a reliable production-kernel panic.
* No structured stale-object leverage: only the one-byte ID field is consumed. No pointer, callback, length, index, refcount, or ownership field is used.
* No controlled reclaim, attacker-shaped replacement, arbitrary write, repeated release, or refcount mutation is demonstrated.
* No local-unprivileged bonus: local access to the query path is plausible, but control over the complete query-plus-device-close sequence below host-admin privilege is unresolved.
* No remote bonus: a remote Bluetooth peer cannot directly invoke the local `getsockopt()` operation.
* NEW52 B5-R does not apply because there is no OOB write, retry accumulation, or later consumption of corrupted descriptors.
* NEW53 B3-PENDING does not apply because there is no shared-backing write.
* NEW54 B4-PENDING does not apply because no authorization decision is bypassed.

3. Reachability analysis

A local process can invoke the `BT_CODEC` query through `sco_sock_getsockopt()`. The competing operation is `hci_dev_close_sync()`, but the supplied evidence does not establish whether the same below-host-admin actor can reliably initiate HCI device closure. Device closure may instead require a privileged management operation or occur naturally during teardown.

The relevant capability namespace and any namespace-scoped complete trigger are not shown. No prior privileged setup, special hardware rarity, or remote trigger is established beyond the need for a Bluetooth HCI device and the affected codec list. The race window is narrow because the close path must free the selected entry after it is fetched but before `entry->id` is read.

4. Primitive and severity interpretation

The exact primitive is a confirmed slab use-after-free read of one byte from a freed codec-list entry. The object is heap-allocated and structured, but the stale operation is shallow and consumes only `entry->id`. It is therefore CLASS_B rather than CLASS_A.

There is no concrete repeated release or refcount operation. The close path frees the entry once, and the reader subsequently reads it without performing another lifetime mutation. Controlled reuse could theoretically strengthen the disclosure, but no reclaim or replacement mechanism is established.

The demonstrated consequence is a KASAN-detected stale read. A limited one-byte disclosure is plausible through the socket option output. Kernel crash or integrity corruption remains possible but unsupported as a reliable primitive. ImportantCandidate is NO because no meaningful write, callback, ownership, refcount, replacement, or boundary-bypass leverage is established. AutoDowngradeAllowed is YES because this is a constrained read-only UAF, although manual review remains appropriate to verify real-world output and privilege reachability.

5. One-sentence report phrase

A race between Bluetooth HCI device closure and a local BT_CODEC query causes a confirmed one-byte slab use-after-free read, but no write, controlled reclaim, reliable crash, or privilege-escalation primitive is established.

6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Confirm whether the stale byte is returned to userspace and whether an ordinary local actor can control both the codec query and HCI close operations.

7. Call-site confidence

Call-site confidence: high

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

Patch: Bluetooth: hci_sync: Serialize local codec list cleanup
Commit: 9f407d52c0d881430d689836d3e7d32aa36f98b5
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9f407d52c0d881430d689836d3e7d32aa36f98b5

Commit description:

hci_dev_close_sync() clears hdev->local_codecs after releasing hdev->lock.
Codec list additions and both traversals in sco_sock_getsockopt() use that
lock, but the close path does not. A close and BT_CODEC query can therefore
interleave as follows:

  hci_dev_close_sync()          sco_sock_getsockopt()
                                hci_dev_lock()
                                fetch codec entry
  hci_codec_list_clear()
    kfree(entry)
                                read entry->id

The reader then accesses an entry which the close path has freed. KASAN
reported:

  BUG: KASAN: slab-use-after-free in sco_sock_getsockopt+0xfa0/0xfe0
  Read of size 1 at addr ffff8881001c3450
  Call Trace:
   sco_sock_getsockopt+0xfa0/0xfe0
   do_sock_getsockopt+0x537/0x7b0
   __sys_getsockopt+0xf2/0x170
  Allocated by task 92:
   hci_codec_list_add.isra.0+0x2c/0x440
   hci_read_codec_capabilities+0x224/0x590
   hci_read_supported_codecs+0x2c2/0x640
  Freed by task 92:
   kfree+0x131/0x3c0
   hci_codec_list_clear+0xd8/0x160
   hci_dev_close_sync+0x92a/0xfa0

Take hdev->lock around the clear operation at its existing point in the
close path. This makes the clear wait for active readers and prevents a new
traversal until the list is empty without changing teardown ordering.

Fixes: b938790 ("Bluetooth: hci_codec: Fix leaking content of local_codecs")
Cc: stable@vger.kernel.org
Signed-off-by: Chengfeng Ye <nicoyip.dev@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/hci_sync.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=9f407d52c0d881430d689836d3e7d32aa36f98b5

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

The original Linux kernel CVE announcement for CVE-2026-98246 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98246

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:L/A:H
  The Best / paranoid CVSS score: 5.8

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: 4

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).