[CVE-2026-72334][MODERATE REGULAR] Bluetooth: ISO: fix malformed ISO_END/CONT handling [ Upstream

[CVE-2026-72334][MODERATE REGULAR] Bluetooth: ISO: fix malformed ISO_END/CONT handling [ Upstream

[AL-KERNEL]

CVE: CVE-2026-72334
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: Bluetooth: ISO: fix malformed ISO_END/CONT handling [ Upstream
Commit: 990e65eb9387c4ddfa7f68782b6644c2c35d489f
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=990e65eb9387c4ddfa7f68782b6644c2c35d489f
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72334
Analysis date: Sat, 15 Aug 2026 10:09:11 -0400
ActionableScore: 4
ActionableScore lower bound: 3
Actionable bucket: Borderline, manual review recommended
Manual review required: YES

Summary:
Malformed Bluetooth ISO_END or ISO_CONT handling can allow malformed adjacent Bluetooth or controller-supplied ISO fragments to leak conn rx_skb or trigger an skb_put panic, causing a kernel denial of service without supported evidence of privilege escalation.

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

The original Linux kernel CVE announcement for CVE-2026-72334 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72334

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 REGULAR
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
======================================================================

CVE-2026-72334	MODERATE	CHECK WITH IMPACT FROM ORIG NN IMPORTANT	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H';*CWE-20;CWE-617;**CWE-400;Other CVSS 'AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '6.5';DESCR 'Malformed Bluetooth ISO fragmentation can leave conn rx_skb allocated or can drive iso_recv into skb_put with an excessive ISO_END length, leading to a kernel panic. A malformed sequence such as ISO_START, ISO_CONT, ISO_START can leak the receive skb, while an overlong ISO_END can crash the host and a too short ISO_END may be accepted incorrectly. For the CVSS the PR:N is used for the paranoid score because an attacker does not need local privileges if malformed ISO data can be delivered over an adjacent Bluetooth link or through an exposed HCI controller path. The issue is not Internet reachable but it is adjacent network reachable for Bluetooth capable targets and practical exploitation depends on ISO support, controller behavior, and the ability to influence malformed ISO fragments. Impact is denial of service via resource leak or kernel crash, with no supported evidence of privilege escalation.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended (with actual score 4)  SKIP CVE-2026-72334 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: 84c24fb151fc1179355296d7ff29129ac7c42129 YES  NO NO unknown 	MAYBE	REMOTE LEAK NETWORK SKB PACKET  DECREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCORELOWERTHAN6 DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	-	-	checked

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

ActionableScore=4
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 4
* Final recommended bucket: **Borderline, manual review recommended**::

## 2. Signal breakdown

Conservative signals:

* Firmware-mediated external influence: +1
  The malformed ISO fragments are described as being sent by the Bluetooth controller. A nearby peer may influence this path only if the controller forwards or produces such malformed HCI ISO sequences.

* Reliable kernel crash / strong DoS: +1
  The commit explicitly states that a too long ISO_END can panic on skb_put.

* Availability impact realistic: +1
  The failure mode is a host kernel panic, not just a rejected packet or local warning.

Paranoid delta:

* Remote reachable / network-triggerable: +2 instead of firmware-mediated +1
  If malformed ISO traffic can be induced by an adjacent Bluetooth peer rather than only by a faulty or malicious local controller, this becomes adjacent-network reachable.

Not awarded:

* No generic memory corruption score. skb_put appears to panic on length validation rather than giving a demonstrated controlled overwrite.
* No LPE score. The patch does not show reclaim, object replacement, callback control, type confusion, or write primitive.
* No confidentiality or integrity impact. The supported impact is leak of conn->rx_skb and kernel panic.

## 3. Reachability analysis

The direct malformed input source is the Bluetooth controller delivering ISO fragments into iso_recv. A local unprivileged process is not clearly required, and the meaningful question is whether a remote adjacent Bluetooth device can cause the controller to emit the malformed ISO_START, ISO_CONT, or ISO_END sequence. This is not Internet reachable. It is potentially adjacent-network reachable on Bluetooth-capable systems with ISO support enabled and relevant controller behavior. Namespaces do not meaningfully reduce the attack requirement because the vulnerable path is below normal socket namespace policy once malformed HCI ISO data reaches the host stack.

## 4. Severity interpretation

This behaves more like a strong DoS / actionable edge Moderate than an Important memory-corruption issue. The realistic demonstrated impact is kernel panic via malformed Bluetooth ISO fragmentation and resource leak of conn->rx_skb. Theoretical memory corruption is not supported strongly enough because the described skb_put path is a panic condition, not a shown attacker-controlled overwrite. Manual review is still justified because Bluetooth is an adjacent external input path and exploitability depends on controller and over-the-air behavior.

## 5. One-sentence report phrase

Malformed Bluetooth ISO_END or ISO_CONT handling can allow malformed adjacent Bluetooth or controller-supplied ISO fragments to leak conn rx_skb or trigger an skb_put panic, causing a kernel denial of service without supported evidence of privilege escalation.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

This should not be auto-closed because it is an adjacent Bluetooth input path with an explicit kernel panic condition. The key manual question is whether a nearby Bluetooth peer can reliably induce the malformed HCI ISO sequence on affected controllers, or whether triggering is limited to faulty or malicious local firmware/controller behavior.

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

Patch: Bluetooth: ISO: fix malformed ISO_END/CONT handling [ Upstream
Commit: 990e65eb9387c4ddfa7f68782b6644c2c35d489f
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=990e65eb9387c4ddfa7f68782b6644c2c35d489f

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=990e65eb9387c4ddfa7f68782b6644c2c35d489f

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

The original Linux kernel CVE announcement for CVE-2026-72334 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72334

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:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 6.5

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: 4

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 REGULAR

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).