[CVE-2026-63945][MODERATE 7.0] Bluetooth: ISO: serialize iso_sock_clear_timer with socket lock

[CVE-2026-63945][MODERATE 7.0] Bluetooth: ISO: serialize iso_sock_clear_timer with socket lock

[AL-KERNEL]

CVE: CVE-2026-63945
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: Bluetooth: ISO: serialize iso_sock_clear_timer with socket lock
Commit: d9cbf7144ec589a3f0cc91f74a1a1af2d2b14afa
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d9cbf7144ec589a3f0cc91f74a1a1af2d2b14afa
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63945
Analysis date: Sun, 19 Jul 2026 22:36:02 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A race in the Bluetooth ISO socket close path can leave `iso_sock_clear_timer()` using an unstable connection pointer while `iso_conn_del()` clears and frees it, causing a NULL dereference or use-after-free and a local kernel crash, with limited but nonzero manual-review concern for broader memory-corruption impact.

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

The original Linux kernel CVE announcement for CVE-2026-63945 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63945

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-2026-63945	MODERATE	CHECK WITH IMPACT FROM ORIG NN MODERATE	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 the Bluetooth ISO socket close path can make iso_sock_clear_timer() use iso_pi conn without holding the socket lock while iso_conn_del can concurrently clear the same connection pointer and drop the final reference. This can lead to a NULL-pointer dereference or a use-after-free when cancel_delayed_work() is called on the stale connection object. For the CVSS the PR:L is used because a local user or local process able to create and operate Bluetooth ISO sockets is needed for triggering, while PR:N is not appropriate for this local socket interface. The issue is not directly network reachable in the IP sense, but it may involve local Bluetooth activity and connection teardown timing. Impact is at least a local denial of service via kernel crash and in the paranoid case may allow confidentiality and integrity impact due to kernel use-after-free memory corruption, so manual review is preferred over automatic closure.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5)	YES	REMOTE NULLPTR INIT UAF NETWORK TIMER HARDWARE KPANIC 	YES	NO	checked

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

ActionableScore=5
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: 4
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum**::

## 2. Signal breakdown

Triggered signals:

* Local unprivileged trigger: +1
  A local process able to create and operate Bluetooth ISO sockets can plausibly trigger the close versus connection teardown race.

* Memory corruption, weak/indirect corruption candidate: +1
  The patch describes a stale `iso_pi(sk)->conn` pointer that may be used after `iso_chan_del()` clears it and drops the final reference. This is a race-dependent UAF candidate, but no attacker-controlled reclaim or overwrite primitive is shown.

* Real lifetime corruption: +1
  The bug is explicitly a lifetime synchronization issue between `iso_sock_clear_timer()` and `iso_conn_del()` / `iso_chan_del()`.

* Reliable kernel crash / strong DoS: +1
  The commit explicitly states possible NULL dereference or UAF when `cancel_delayed_work()` is called on an unstable connection pointer.

Paranoid-only signal:

* Manual-review UAF concern: +1
  The stale pointer is used as an embedded workqueue object address. Even though no reclaim primitive is demonstrated, kernel lifetime bugs in socket teardown code should not be auto-closed without review.

Limiting factors:

* Hard or unreliable race / special timing required: relevant, but not fully subtracting in the paranoid score because the race is between close and connection deletion paths that may be practically stressable.
* Race-UAF downgrade rule applies. No demonstrated reclaim, stale object replacement, write-after-free, type confusion, callback control, or refcount takeover. This prevents treating it as a strong Important-class memory corruption by default.

## 3. Reachability analysis

The bug is locally reachable through Bluetooth ISO socket operations. It is not IP-network reachable and should not receive the remote/network-triggerable bonus. A nearby Bluetooth peer or local Bluetooth activity may help create teardown timing, but the main attacker model still requires a local process interacting with the Bluetooth ISO socket interface.

Privileges are likely PR:L in CVSS terms rather than PR:N, because local code execution or a local process context is needed. Full host root is not inherently required for ordinary socket close behavior, although practical reachability depends on whether Bluetooth ISO sockets are enabled, whether a Bluetooth controller is present, and whether the environment exposes Bluetooth devices to the attacker. Containers usually do not expose host Bluetooth devices by default, so container reachability is configuration-dependent.

## 4. Severity interpretation

This is more than an ordinary low-risk cleanup because the patch fixes an explicit race that can produce NULL dereference or use-after-free in kernel Bluetooth socket code. Realistic impact is most clearly local denial of service through a kernel crash or Oops.

Theoretical memory corruption potential exists because the stale connection pointer may reference freed memory, but the patch does not show attacker-controlled reclaim, controlled replacement, write primitive, callback hijack, or type confusion. Therefore, this should be treated as Actionable Moderate for triage, not automatically as Strong Important.

## 5. One-sentence report phrase

A race in the Bluetooth ISO socket close path can leave `iso_sock_clear_timer()` using an unstable connection pointer while `iso_conn_del()` clears and frees it, causing a NULL dereference or use-after-free and a local kernel crash, with limited but nonzero manual-review concern for broader memory-corruption impact.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: the issue is an explicit race-dependent UAF candidate in kernel socket lifetime handling. The conservative impact is DoS, but stale pointer use on a freed connection object is sufficient to require manual review before auto-closing.

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

Patch: Bluetooth: ISO: serialize iso_sock_clear_timer with socket lock
Commit: d9cbf7144ec589a3f0cc91f74a1a1af2d2b14afa
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d9cbf7144ec589a3f0cc91f74a1a1af2d2b14afa

Commit description:

iso_sock_close() calls iso_sock_clear_timer() before acquiring
lock_sock(sk).

iso_sock_clear_timer() reads iso_pi(sk)->conn twice without the
socket lock held:

    if (!iso_pi(sk)->conn)
        return;
    cancel_delayed_work(&iso_pi(sk)->conn->timeout_work);

Concurrently, iso_conn_del() executes under lock_sock(sk) and calls
iso_chan_del(), which sets iso_pi(sk)->conn to NULL and may result in
the final reference to the connection being dropped:

    CPU0                         CPU1
    ----                         ----
    iso_sock_clear_timer()
      if (conn != NULL) ...      lock_sock(sk)
                                   iso_chan_del()
                                   iso_pi(sk)->conn = NULL
      cancel_delayed_work(conn)  /* NULL deref or UAF */

iso_pi(sk)->conn is not stable across the unlock window, causing a
NULL pointer dereference or use-after-free.

Serialize iso_sock_clear_timer() with the socket lock by moving it
inside lock_sock()/release_sock(), matching the pattern used in
iso_conn_del() and all other call sites.

Fixes: ccf74f2 ("Bluetooth: Add BTPROTO_ISO socket type")
Cc: stable@vger.kernel.org
Signed-off-by: Muhammad Bilal <meatuni001@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/iso.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=d9cbf7144ec589a3f0cc91f74a1a1af2d2b14afa

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

The original Linux kernel CVE announcement for CVE-2026-63945 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63945

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: 4
  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: 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 alexanjelausa@gmail.com (and both
send reply to CVE record itself too and see "reply" button below for howto reply).