[CVE-2026-53071][IMPORTANT] Bluetooth: l2cap: Add missing chan lock in l2cap_ecred_reconf_rsp [ Upstream

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

CVE: CVE-2026-53071
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: Bluetooth: l2cap: Add missing chan lock in l2cap_ecred_reconf_rsp [ Upstream
Commit: 96dca51715d86559ed6ed8028e5445cecb80f3ae
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=96dca51715d86559ed6ed8028e5445cecb80f3ae
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53071
Analysis date: Wed, 24 Jun 2026 15:24:00 -0400
ActionableScore: 7
ActionableScore lower bound: 5
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A remote BLE peer in radio range can trigger an L2CAP ECRED reconfiguration race where `l2cap_chan_del()` runs without the required channel lock and lifetime hold, potentially corrupting the channel list and causing at least a kernel crash, with UAF-style impact requiring manual review.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-53071 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53071

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-2026-53071	IMPORTANT	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-667;CWE-362;*CWE-416;Other CVSS 'AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7.5';DESCR 'Bluetooth L2CAP ECRED reconfiguration response handling can call l2cap_chan_del() without holding the channel lock while another thread may be iterating the same channel list. A remote BLE peer in radio range can send a crafted ECRED reconfiguration response and trigger a race that may corrupt the L2CAP channel list, leading at least to a kernel crash or connection state corruption. For the CVSS the PR:N is used because the attacker does not need a local account on the target and only needs Bluetooth reachability as a peer device. The issue is adjacent network reachable rather than Internet reachable because Bluetooth radio proximity is required. Impact is at least denial of service, and in the paranoid case may include confidentiality or integrity impact due to kernel memory corruption or UAF style behavior. For the paranoid score, choose the highest still defensible interpretation supported by the bug class and patch context, with preference for manual review sensitivity over autoclosed false negatives.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 7)	YES	REMOTE SIMPLEFIX NETWORK HARDWARE KPANIC  KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=7
ActionableScoreLower=5

## 1. ActionableScore

* Conservative score: 5
* Paranoid score: 7
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Remote reachable / network-triggerable: +2. A remote BLE peer in radio range can send the crafted L2CAP ECRED reconfiguration response.
* Memory corruption, weak/indirect corruption candidate: +1. The commit describes channel list corruption due to calling `l2cap_chan_del()` without the required channel lock.
* Real lifetime corruption: +1. The fix adds both `l2cap_chan_hold()` and `l2cap_chan_put()`, which indicates a lifetime/refcount protection gap around deletion.
* Reliable kernel crash / strong DoS: +1. Concurrent deletion and iteration of a kernel channel list can realistically lead to list corruption, crash, or connection-state corruption.
* Broad/default/common subsystem exposure: +1. Bluetooth is a broadly deployed subsystem on many Linux systems, although practical exposure depends on Bluetooth being enabled and reachable.
* Hard or unreliable race / special timing required: -1. Exploitation requires hitting a concurrency window while another thread is iterating the channel list.

Paranoid additions:

* Upgrade weak corruption to stronger memory-corruption concern: +1 delta. The combination of unlocked deletion, missing lifetime hold, and concurrent list iteration makes UAF-style behavior technically plausible.
* Weak LPE concern: +1. No controlled reclaim or overwrite primitive is demonstrated, but kernel list/lifetime corruption from an adjacent remote input path is enough to require manual review.

Not counted separately:

* Confidentiality and integrity impact were not independently added to avoid double-counting the same corruption primitive. They remain plausible only in the paranoid interpretation.

## 3. Reachability analysis

The trigger is adjacent-network reachable through Bluetooth/BLE, not Internet-routable IP networking. The attacker does not need a local user account on the target, so practical PR is none in CVSS terms, but the attacker must be within Bluetooth radio range and able to interact as a BLE/L2CAP peer.

Namespaces and containers do not materially reduce the attacker requirement because the entry point is wireless protocol input rather than a local namespace-controlled interface. Exposure depends on Bluetooth being enabled, the affected L2CAP ECRED path being available, and a realistic peer interaction reaching `l2cap_ecred_reconf_rsp()`.

## 4. Severity interpretation

This is not an ordinary Moderate cleanup bug. The conservative interpretation is an actionable Moderate because it is remotely reachable over Bluetooth and can corrupt kernel channel-list state under a race.

The realistic demonstrated impact is likely DoS or connection-state corruption. The theoretical worst case is more serious because missing locking and missing lifetime protection around `l2cap_chan_del()` can plausibly become UAF-style kernel memory corruption. No arbitrary write, controlled reclaim, callback hijack, or reliable privilege-escalation primitive is demonstrated by the patch, so the Important classification should be treated as a strong candidate rather than confirmed LPE/RCE.

## 5. One-sentence report phrase

A remote BLE peer in radio range can trigger an L2CAP ECRED reconfiguration race where `l2cap_chan_del()` runs without the required channel lock and lifetime hold, potentially corrupting the channel list and causing at least a kernel crash, with UAF-style impact requiring manual review.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: this is an adjacent-network reachable race in a kernel protocol parser with explicit list corruption and added lifetime protection in the fix. It should not be auto-closed as ordinary DoS because the patch context supports plausible UAF-style memory corruption even though a concrete privilege-escalation primitive is not demonstrated.

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UPSTREAM PATCH SUMMARY
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Patch: Bluetooth: l2cap: Add missing chan lock in l2cap_ecred_reconf_rsp [ Upstream
Commit: 96dca51715d86559ed6ed8028e5445cecb80f3ae
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=96dca51715d86559ed6ed8028e5445cecb80f3ae

Changed files:
  net/bluetooth/l2cap_core.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=96dca51715d86559ed6ed8028e5445cecb80f3ae

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

The original Linux kernel CVE announcement for CVE-2026-53071 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53071

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:A/AC:H/PR:N/UI:N/S:U/C:L/I:L/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: 5
  Paranoid ActionableScore: 7

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: YES
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).