[CVE-2026-74536][LOW] Bluetooth: ISO: fix leaking sk after socket release [ Upstream

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

CVE: CVE-2026-74536
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: Bluetooth: ISO: fix leaking sk after socket release [ Upstream
Commit: 96ed3c772c08e7a91c399567f412618e43231023
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=96ed3c772c08e7a91c399567f412618e43231023
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74536
Analysis date: Sat, 15 Aug 2026 13:45:55 -0400
ActionableScore: 2
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate / Low-like. NO MANUAL CHECK REQUIRED COULD BE AUTOCLOSED
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-74536 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74536

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: LOW
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-2026-74536	LOW	CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';*CWE-401;*CWE-772;CWE-362;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'Bluetooth ISO socket cleanup can leak the underlying sock object because iso_sock_kill returns early after sock_orphan sets SOCK_DEAD, so the final socket reference is not dropped and iso_sock_destruct is not reached. A local process that can create and close BTPROTO_ISO sockets, especially with concurrent connection teardown, can accumulate leaked socket objects and eventually exhaust kernel memory or related Bluetooth socket resources. For the CVSS the PR:L is used for the paranoid score because reliable triggering requires local code execution or a low privileged process with access to Bluetooth ISO sockets rather than unauthenticated remote packet traffic. The issue is not directly network reachable, although a Bluetooth peer may influence connection teardown in deployments that use ISO connections. Impact is denial of service via resource exhaustion. No concrete arbitrary write or information leak primitive is shown, so the class remains resource leak and cleanup race rather than confirmed privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like. NO MANUAL CHECK REQUIRED COULD BE AUTOCLOSED (with actual score 2)	YES	REMOTE LEAK UAF NETWORK TEST  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	YES	NO	checked

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

ActionableScore=2

1. ActionableScore
* Conservative score: 2
* Paranoid score: 3 if sustained local abuse of Bluetooth ISO socket creation and teardown is considered highly practical in the target environment.
* Final recommended bucket: **Ordinary Moderate / Low-like. NO MANUAL CHECK REQUIRED COULD BE AUTOCLOSED**

2. Signal breakdown
* Local unprivileged trigger: +1. A local process that can create and close BTPROTO_ISO sockets can plausibly trigger the reference leak.
* Real lifetime corruption: +1. The bug is a socket reference lifetime issue where the final sk reference is not dropped and iso_sock_destruct is not reached.
* Availability impact realistic: +1. Repeated triggering can leak sock objects and may eventually exhaust kernel memory or Bluetooth socket resources.
* Rare AND difficult-to-reach subsystem/configuration: -1. Bluetooth ISO depends on Bluetooth ISO support and relevant runtime availability, so exposure is narrower than core networking.
* No generic memory corruption: +0. The patch shows a leak/refcount cleanup bug, not UAF reuse, double free, OOB write, type confusion, or attacker-controlled overwrite.
* No privilege escalation plausible signal: +0. There is no demonstrated reclaim, stale callback, write-after-free, object replacement, or sensitive data access primitive.
* No remote/network-triggerable signal: +0. A Bluetooth peer may influence teardown, but reliable triggering appears to require local socket activity.

3. Reachability analysis
A local user or process with access to Bluetooth ISO sockets is the main realistic trigger. This is not an unauthenticated network packet parsing issue and should not be scored as remotely reachable. Namespaces or containers may matter only if the environment delegates Bluetooth socket access to less trusted workloads. The path is not as broadly exposed as TCP/IP or netfilter and depends on Bluetooth ISO support being enabled and usable.

4. Severity interpretation
This behaves like an ordinary Moderate or Low-like resource lifetime bug rather than an Important-class kernel vulnerability. The realistic impact is local denial of service through resource exhaustion after repeated socket creation and release. Theoretical concern is limited because the patch does not show memory reuse after free, attacker-controlled corruption, callback control, information disclosure, or a privilege escalation path.

5. One-sentence report phrase
Bluetooth ISO socket cleanup can leak the underlying sock object after socket release because iso_sock_kill incorrectly treats SOCK_DEAD as a kill marker, allowing a local process with BTPROTO_ISO access to cause resource exhaustion and denial of service.

6. Manual review recommendation
NO MANUAL CHECK NEEDED. This is a resource leak and cleanup race without a demonstrated memory corruption or privilege escalation primitive, and the practical score remains below the actionable Moderate threshold.

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

Patch: Bluetooth: ISO: fix leaking sk after socket release [ Upstream
Commit: 96ed3c772c08e7a91c399567f412618e43231023
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=96ed3c772c08e7a91c399567f412618e43231023

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=96ed3c772c08e7a91c399567f412618e43231023

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

The original Linux kernel CVE announcement for CVE-2026-74536 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74536

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:L/PR:L/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 5.5

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: unknown
  Paranoid ActionableScore: 2

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: LOW
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): LOW

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).