* [CVE-2026-99015][MODERATE 7.0] Bluetooth: hci_sock: Serialize dead-device detachment
@ 2026-10-27 4:53 21% AL-KERNEL
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From: AL-KERNEL @ 2026-10-27 4:53 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-99015
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: Bluetooth: hci_sock: Serialize dead-device detachment
Commit: 37cef0c8fb537f40600910d2c2e5f2d5509305f3
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=37cef0c8fb537f40600910d2c2e5f2d5509305f3
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99015
Analysis date: Tue, 27 Oct 2026 00:53:00 -0400
ActionableScore: 4
ActionableScore lower bound: unknown
Actionable bucket: Borderline / manual review recommended
Manual review required: YES
Summary:
Concurrent HCI socket rebinding and controller detachment can leave monitor replay using a freed `hci_dev`, causing a NULL dereference or crash-capable UAF.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-99015 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99015
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-2026-99015 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-99015 CHECK WITH IMPACT FROM ORIG NN IMPORTANT | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=6 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;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 hci_sock_bind can detach an HCI socket and drop the final device reference while monitor replay or socket delivery still uses the old hdev pointer. The demonstrated primitives are a NULL pointer dereference and a retained pointer use after free when create_monitor_ctrl_open reads hdev id, with kernel crash as the immediate impact. For the CVSS the PR:L value reflects that triggering requires a local process with access to the Bluetooth HCI socket interface, while capability checks and control over device unregister may vary by socket channel and deployment. AC:H reflects the required race with controller unregister and concurrent replay or delivery. Impact is at least a local denial of service and in the worst defensible case may include confidentiality or integrity impact if the freed hci_dev object is reused, so the UAF requires manual review. The issue is not directly network reachable through ordinary Bluetooth traffic. Automated impact decision path. The original SimpleNet classifier selected IMPORTANT. The primary LLM estimated paranoid CVSS 7 and the production ActionableScore returned 4 with recommendation Borderline / manual review recommended. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage IMPORTANT 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 LOWERED_FROM_HIGH_BASED_ON_NULLPTR. The independent weaker Aegis shadow evaluated CVSS 2.4 and ActionableScore 6 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 Borderline / manual review recommended (with actual score 4) MAYBE REMOTE DANGER NULLPTR RACE UAF NETWORK KERNEL_PANIC_PLUS_UAF HARDWARE LINUS KPANIC KPANIC LOWERED_FROM_HIGH_BASED_ON_NULLPTR - - checked
======================================================================
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 base score: 2.
* Conservative score: 4. Real-UAF floor 4 applied: 2 -> 4.
* Raw paranoid score: 2.
* Paranoid score: 4. No additional exploit primitive supports a paranoid increment; Real-UAF floor 4 applied.
* Final recommended bucket: **Borderline / manual review recommended**::
2. Signal breakdown
* +2 — Real active-object UAF: replay can retain `hdev` while bind clears the socket pointer and drops the final device reference.
* +1 — Plausible kernel crash: KASAN reports the corresponding NULL dereference; retained-pointer execution can instead dereference freed `hci_dev`.
* -1 — Hard race: exploitation requires controller unregistration, rebinding, and concurrent replay or delivery within the detach window.
* No controlled reclaim, attacker-shaped replacement object, post-free write, callback consumption, repeated refcount mutation, arbitrary access, or disclosure is shown.
* No extra availability point: it would duplicate the same crash.
* The stale use reads `hdev->id`; object complexity alone does not establish structured stale-object leverage.
* The separate stale-binding delivery behavior can queue a frame after detach/rebind, but no protected recipient, namespace boundary, or security-policy bypass is established.
3. Reachability analysis
A local process can invoke socket bind, but the evidence does not establish who can perform the complete sequence, especially controller unregistration and monitor-control replay. The relevant HCI channel capability checks, capability namespace, and whether a non-host-admin actor controls all stages are absent. Thus host-admin and namespace-scoped privilege remain unknown. Ordinary Bluetooth traffic is not a direct remote trigger. The race appears timing-sensitive and may depend on device teardown or privileged control activity.
4. Primitive and severity reading
The primitive is an active structured `hci_dev` lifetime violation, not fixed stale storage: a reader can retain the old pointer beyond the final `hci_dev_put()` and then read `hdev->id`. This is CLASS_B. The demonstrated effect is NULL/UAF dereference and kernel crash; useful post-reclaim behavior is unproven. There is no second lifetime/refcount mutation. ImportantCandidate is NO because the supplied evidence supports a constrained crash-oriented stale read without material reuse or boundary leverage. Auto-downgrade remains allowed, though manual review is advisable due to the genuine UAF.
5. One-sentence report phrase
Concurrent HCI socket rebinding and controller detachment can leave monitor replay using a freed `hci_dev`, causing a NULL dereference or crash-capable UAF.
6. Manual review advice
MANUAL CHECK RECOMMENDED
Confirm HCI channel permissions, control over controller unregistration, and whether stale frame delivery crosses any socket or namespace trust boundary.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: Bluetooth: hci_sock: Serialize dead-device detachment
Commit: 37cef0c8fb537f40600910d2c2e5f2d5509305f3
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=37cef0c8fb537f40600910d2c2e5f2d5509305f3
Commit description:
Rebinding an HCI socket after its controller is unregistered can race
monitor control replay and crash the kernel. hci_sock_bind() clears
hci_pi(sk)->hdev and drops the device reference under only the socket
lock, whereas send_monitor_control_replay() holds hci_sk_list.lock for
reading.
Replay can observe a non-NULL hdev, then bind can clear it and drop the
last reference before create_monitor_ctrl_open() reads hdev->id. This
can cause a NULL pointer dereference if the pointer is reloaded, or a
use-after-free if the old pointer is retained.
The kernel reported:
KASAN: null-ptr-deref in range [0x0000000000000068-0x000000000000006f]
RIP: 0010:create_monitor_ctrl_open+0x579/0x800
Call Trace:
hci_sock_bind+0xd96/0x1190
__sys_bind+0x166/0x200
__x64_sys_bind+0x6d/0xb0
do_syscall_64+0xdd/0x4a0
entry_SYSCALL_64_after_hwframe+0x77/0x7f
The same missing serialization lets hci_send_to_sock() select a socket
for the old device and queue its frame after bind has detached the socket
or installed a new binding.
Take hci_sk_list.lock for writing when clearing the device pointer and
resetting the socket state. This waits for existing replay and delivery
readers to finish before detachment and prevents later readers from
using the old binding. Keep hci_dev_put() outside the critical section
because the final device release can sleep.
Fixes: e044809 ("Bluetooth: defer cleanup of resources in hci_unregister_dev()")
Cc: [email protected]
Assisted-by: GPT-6 Astra
Signed-off-by: Chengfeng Ye <[email protected]>
Signed-off-by: Luiz Augusto von Dentz <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
net/bluetooth/hci_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=37cef0c8fb537f40600910d2c2e5f2d5509305f3
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-99015 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99015
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: 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: 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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