[CVE-2026-74541][MODERATE 7.0] Bluetooth: ISO: clear iso_data always when detaching conn from hcon [ Upstream

[CVE-2026-74541][MODERATE 7.0] Bluetooth: ISO: clear iso_data always when detaching conn from hcon [ Upstream

[AL-KERNEL]

CVE: CVE-2026-74541
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: Bluetooth: ISO: clear iso_data always when detaching conn from hcon [ Upstream
Commit: cc1d39946d62bc568551dfb81149724de1e91338
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=cc1d39946d62bc568551dfb81149724de1e91338
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74541
Analysis date: Sat, 15 Aug 2026 18:54:23 -0400
ActionableScore: 6
ActionableScore lower bound: 5
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A stale hcon iso_data pointer in the Bluetooth ISO socket disconnect path can survive after conn hcon is cleared, allowing later cleanup to hit a slab use-after-free and causing at least a local kernel crash, with weak privilege-escalation concern requiring manual review.

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

The original Linux kernel CVE announcement for CVE-2026-74541 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74541

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-2026-74541	MODERATE	CHECK WITH IMPACT FROM ORIG NN IMPORTANT	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-416;CWE-825;*CWE-664;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'A stale pointer use-after-free can occur in the Bluetooth ISO connection lifecycle because iso_sock_disconn() cleared conn hcon without clearing the reverse hcon iso_data pointer. A later cleanup path such as iso_sock_release() followed by hci_abort_conn_sync() may dereference the stale iso_data pointer in iso_conn_hold_unless_zero and trigger a KASAN slab-use-after-free. For the CVSS the PR:L is used because reliable triggering requires local code execution or a local process able to create and close Bluetooth ISO sockets on the target. The issue is not directly reachable over IP networking, although a Bluetooth peer in radio range may influence connection timing in real deployments. Impact is at least local denial of service via kernel crash. For the paranoid score, this is treated as a kernel memory corruption candidate and may allow confidentiality or integrity impact or local privilege escalation in worst case, so manual review is preferred over automatic closure.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 7)	YES	REMOTE DANGER UAF NETWORK KPANIC  DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFKP	YES	NO	checked

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

ActionableScore=6
ActionableScoreLower=5

## 1. ActionableScore

* Conservative score: 5
* Paranoid score: 6
* Final recommended bucket: **Actionable Moderate at minimum**

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1. A local process able to create and release Bluetooth ISO sockets can reach the affected lifecycle path.
* Memory corruption, strong corruption primitive: +2. The commit explicitly reports KASAN slab-use-after-free.
* Real lifetime corruption: +1. The bug is a stale reverse pointer lifetime issue where hcon->iso_data can outlive conn->hcon detachment.
* Reliable kernel crash / strong DoS: +1. The reported path reaches slab-use-after-free in iso_conn_hold_unless_zero after iso_sock_release() followed by hci_abort_conn_sync().

Paranoid additional signal:

* Weak LPE concern: +1. The stale pointer is later used in a hold-unless-zero style path, so object reuse/refcount interaction is a plausible manual-review concern, but there is no demonstrated attacker-controlled reclaim, write primitive, callback control, or type confusion.

Not counted:

* Remote reachable / network-triggerable: +0. This is not directly reachable over IP networking.
* Bluetooth radio peer influence: not counted as full remote reachability. A peer may affect connection timing, but the reliable trigger still appears to require local socket lifecycle control.
* Hard race subtraction: 0. The provided text describes a concrete lifecycle sequence rather than only an extremely narrow timing race.

## 3. Reachability analysis

The most realistic attacker is a local user or local process with access to Bluetooth ISO socket operations on a system with Bluetooth ISO support enabled. Namespaces may matter if Bluetooth socket access is delegated into a container or service context, but this should not be treated as full host-root access by default. The path is not a general network packet-processing path and is not directly reachable from IP networking. Practical exploitation depends on Bluetooth support, ISO feature availability, and the ability to drive socket release plus connection abort behavior.

Call-site confidence: high, because the patch and commit message identify iso_sock_disconn(), iso_sock_release(), hci_abort_conn_sync(), and the KASAN UAF site.

## 4. Severity interpretation

This is more than an ordinary Moderate because it is a real kernel UAF rather than a pure NULL dereference, warning, or resource leak. Realistic impact is at least local kernel crash / DoS. Privilege escalation is not demonstrated, but the stale pointer plus refcount/lifetime use is enough to avoid auto-closure and justify manual review. It is not a Strong Important candidate on the conservative evidence alone because there is no shown reclaim strategy, write-after-free, callback dispatch, type confusion, or arbitrary write primitive.

## 5. One-sentence report phrase

A stale hcon iso_data pointer in the Bluetooth ISO socket disconnect path can survive after conn hcon is cleared, allowing later cleanup to hit a slab use-after-free and causing at least a local kernel crash, with weak privilege-escalation concern requiring manual review.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: this is an explicitly reported KASAN slab-use-after-free in kernel Bluetooth ISO lifetime handling. The demonstrated impact is DoS, but UAF class and stale pointer reuse make it unsuitable for automatic closure.

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

Patch: Bluetooth: ISO: clear iso_data always when detaching conn from hcon [ Upstream
Commit: cc1d39946d62bc568551dfb81149724de1e91338
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=cc1d39946d62bc568551dfb81149724de1e91338

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=cc1d39946d62bc568551dfb81149724de1e91338

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

The original Linux kernel CVE announcement for CVE-2026-74541 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74541

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:N/I:N/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: 5
  Paranoid ActionableScore: 6

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).