[CVE-2026-53358][MODERATE 7.0] Bluetooth: L2CAP: use chan timer to close channels in cleanup_listen() [ Upstream

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

CVE: CVE-2026-53358
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: Bluetooth: L2CAP: use chan timer to close channels in cleanup_listen() [ Upstream
Commit: 3634cbdc2eb414b69ffa752ddbe5e0458518e321
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3634cbdc2eb414b69ffa752ddbe5e0458518e321
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53358
Analysis date: Thu, 02 Jul 2026 09:52:22 -0400
ActionableScore: 5
ActionableScore lower bound: 3
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A race in Bluetooth L2CAP listener cleanup can close or tear down channels concurrently with `l2cap_conn_del()`, creating a UAF candidate and likely kernel crash path, with local triggerability and possible adjacent Bluetooth influence but no demonstrated privilege escalation primitive.

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

The original Linux kernel CVE announcement for CVE-2026-53358 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53358

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.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-53358	MODERATE	CHECK	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H';*CWE-416;CWE-362;CWE-667;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';BEST CVSS score: '7.5';DESCR 'Bluetooth L2CAP cleanup_listen can race with l2cap_conn_del because the old path closed a channel directly while holding the parent sk_lock and without taking conn lock in the established lock order. This can leave channel and socket cleanup racing with connection teardown and is a UAF candidate in l2cap_sock_cleanup_listen versus l2cap_conn_del. A local user with Bluetooth socket access can trigger the path by creating and closing L2CAP listening sockets, while an adjacent Bluetooth peer can contribute to connection teardown timing. For the CVSS the PR:N is used for the paranoid adjacent attack model where the attacker is a nearby Bluetooth peer interacting with an exposed L2CAP service without local credentials. Impact is at least denial of service via kernel crash and in the worst case may allow confidentiality and integrity impact due to UAF based memory corruption, so manual review is required. YES REQUIRES MANUAL CHECK';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 4)	YES	REMOTE INIT RACE UAF NETWORK TIMER  INCREASED_TO_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCORELOWERTHAN7 DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	NO	NO	guess

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ACTIONABLESCORE ANALYSIS
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ActionableScore=5
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 5
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1. A local user with access to Bluetooth L2CAP sockets can plausibly create and close listening sockets and drive `cleanup_listen()`.
* Memory corruption, weak/indirect corruption candidate: +1. The commit explicitly references a prior UAF fix and a race between `l2cap_sock_cleanup_listen()` and `l2cap_conn_del()`, but the patch does not show attacker-controlled reclaim, overwrite, type confusion, callback dispatch, or refcount takeover.
* Real lifetime corruption: +1. The bug is in channel/socket lifetime handling and races with connection teardown.
* Reliable kernel crash / strong DoS: +1. A UAF or double put in Bluetooth socket cleanup can realistically crash the kernel.
* Hard or unreliable race / special timing required: -1. The issue depends on a race between listener cleanup and connection deletion.

Conservative total: 3.

Paranoid additional interpretation:

* Remote reachable / adjacent Bluetooth-triggerable influence: +2. A nearby Bluetooth peer may contribute to connection setup or teardown timing against an exposed L2CAP service, although this is adjacent Bluetooth reachability rather than Internet reachability.
* Broad/default/common exposure: +1. Bluetooth is a common desktop/laptop subsystem, but not universally enabled on servers.

Paranoid total would reach 5 and is capped appropriately for a race-dependent UAF without a demonstrated reclaim or overwrite primitive.

Not awarded:

* Strong LPE plausibility: +0. No attacker-controlled reclaim, stale callback, writable UAF, arbitrary write, or object replacement primitive is shown.
* Confidentiality / Integrity impact: +0 conservative. The patch supports UAF concern, but not a demonstrated disclosure or write primitive.
* Dirty-Pipe-like / page-cache corruption: +0. Not applicable.

Call-site confidence: high. The affected function and the relevant close/teardown path are visible in the provided patch and commit text.

## 3. Reachability analysis

The conservative trigger is local and likely available to an unprivileged process that can use Bluetooth L2CAP sockets. The vulnerable path is reached during cleanup of accepted listening sockets while connection teardown may run concurrently.

The paranoid reachability model considers a nearby Bluetooth peer interacting with an exposed L2CAP service. That peer may influence connection teardown timing, but reliable exploitation still likely depends on a local service or local socket lifecycle behavior. This is not Internet remote in the usual CVSS AV:N sense.

Namespaces and containers may matter if Bluetooth socket access is delegated into a container or sandbox. In normal host deployments, Bluetooth access is often local-user reachable on desktops, but not necessarily present or enabled on servers.

## 4. Severity interpretation

This behaves above an ordinary Moderate because it is a real lifetime/race bug in kernel Bluetooth socket/channel cleanup and the commit context explicitly ties it to UAF handling.

It does not reach a strong Important score conservatively because the patch does not demonstrate a practical LPE primitive such as controlled reclaim, write-after-free, callback corruption, type confusion, or refcount takeover. Realistic impact is most clearly kernel crash / DoS. The paranoid score is Actionable Moderate because adjacent Bluetooth influence plus UAF-class lifetime corruption should not be auto-closed without manual review.

## 5. One-sentence report phrase

A race in Bluetooth L2CAP listener cleanup can close or tear down channels concurrently with `l2cap_conn_del()`, creating a UAF candidate and likely kernel crash path, with local triggerability and possible adjacent Bluetooth influence but no demonstrated privilege escalation primitive.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: the issue is a Bluetooth kernel lifetime race with explicit UAF context, possible adjacent attack influence, and enough uncertainty around socket/channel object reuse to require human review even though the demonstrated impact is primarily DoS.

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

Patch: Bluetooth: L2CAP: use chan timer to close channels in cleanup_listen() [ Upstream
Commit: 3634cbdc2eb414b69ffa752ddbe5e0458518e321
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3634cbdc2eb414b69ffa752ddbe5e0458518e321

Changed files:
  net/bluetooth/l2cap_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=3634cbdc2eb414b69ffa752ddbe5e0458518e321

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

The original Linux kernel CVE announcement for CVE-2026-53358 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53358

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:H/I:H/A:H
  The Best / paranoid CVSS vector: AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 7.5

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: 3
  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: NO
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 alexanjelausa@gmail.com (and both
send reply to CVE record itself too and see "reply" button below for howto reply).