[CVE-2026-53253][MODERATE 7.0] Bluetooth: bnep: reject short frames before parsing [ Upstream

[CVE-2026-53253][MODERATE 7.0] Bluetooth: bnep: reject short frames before parsing [ Upstream

[AL-KERNEL]

CVE: CVE-2026-53253
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: Bluetooth: bnep: reject short frames before parsing [ Upstream
Commit: 0ef2ea86c82b2615902d085cd5a586fe9f58994f
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0ef2ea86c82b2615902d085cd5a586fe9f58994f
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53253
Analysis date: Thu, 25 Jun 2026 10:08:43 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A malformed short Bluetooth BNEP SDU can trigger an out-of-bounds read in `bnep_rx_frame()` before fixed fields are length-validated, allowing an adjacent Bluetooth peer to cause kernel DoS and requiring manual triage due to network reachability.

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

The original Linux kernel CVE announcement for CVE-2026-53253 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53253

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.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-53253	MODERATE	CHECK	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H';CWE-125;*CWE-20;CWE-130;Other CVSS 'AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7.1';DESCR 'A short BNEP SDU can reach bnep_rx_frame before the parser has proven that the fixed fields are present. The code reads the packet type byte and for control packets also reads the control opcode and setup UUID size byte before sufficient length validation, which can trigger a slab out of bounds read in kernel Bluetooth packet parsing. A remote Bluetooth BNEP peer can trigger this by sending a malformed short frame, causing a kernel crash or KASAN report. For the CVSS the PR:N is used because no local user access on the target is required once the attacker can act as a Bluetooth BNEP peer. The issue is adjacent network reachable rather than Internet reachable because Bluetooth proximity and BNEP connectivity are required. Impact is primarily denial of service. For the paranoid score, limited confidentiality impact is kept because the primitive is an out of bounds read, but there is no evidence of an out of bounds write or UAF based privilege escalation.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5)	YES	REMOTE READ KASAN OOB NETWORK SKB KPANIC PACKET 	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=5
ActionableScoreLower=4

## 1. ActionableScore

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

## 2. Signal breakdown

* Remote reachable / network-triggerable: +2. A malformed BNEP SDU can be sent by a Bluetooth BNEP peer, so this is adjacent-network reachable rather than Internet reachable.
* Reliable kernel crash / strong DoS: +1. The commit includes a reproduced KASAN slab-out-of-bounds read in `bnep_rx_frame()`, and malformed protocol input can reach the vulnerable parser.
* Availability impact realistic: +1. A peer that can send malformed short frames can likely repeat the trigger and disrupt the Bluetooth networking path or crash kernels with hardening or panic-on-report behavior.
* Paranoid limited confidentiality concern: +1. The primitive is an out-of-bounds read of one byte in kernel packet parsing, so limited C impact is defensible for triage sensitivity, but there is no demonstrated user-visible leak.
* No strong memory corruption bonus. The patch shows read-before-length-check and slab OOB read, not OOB write, UAF, double free, refcount misuse, callback corruption, or type confusion.
* No LPE bonus. There is no demonstrated reclaim, overwrite, stale callback, arbitrary write, or privilege-escalation primitive.
* No rare-subsystem subtraction in paranoid scoring. BNEP is not Internet exposed and requires Bluetooth/BNEP connectivity, but it is still a real kernel network parser reachable by an external peer.

## 3. Reachability analysis

A remote nearby attacker can trigger the bug if they can act as a Bluetooth BNEP peer and deliver malformed short BNEP frames to an established or reachable BNEP path. No local user account on the target is required for the adjacent-network attack model. The path is not broadly Internet exposed and normally depends on Bluetooth being enabled plus BNEP/PAN usage, so exposure is narrower than TCP/IP core networking. Containers and namespaces are not the main factor here because the relevant attacker position is external Bluetooth peer access, not local syscall access.

## 4. Severity interpretation

This behaves above ordinary Moderate because it is externally reachable over an adjacent network protocol and affects kernel packet parsing. Realistic demonstrated impact is DoS via KASAN-detected slab OOB read and possible crash. Theoretical confidentiality impact is limited and only used for the paranoid score because the bug is an invalid read, but the patch does not show a disclosure channel or write primitive. It is not a strong Important candidate for LPE because there is no UAF, overwrite, object lifetime corruption, or controlled memory corruption primitive.

## 5. One-sentence report phrase

A malformed short Bluetooth BNEP SDU can trigger an out-of-bounds read in `bnep_rx_frame()` before fixed fields are length-validated, allowing an adjacent Bluetooth peer to cause kernel DoS and requiring manual triage due to network reachability.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: adjacent-network reachable kernel parser bug with a concrete slab out-of-bounds read primitive, even though realistic impact appears primarily DoS and not proven privilege escalation.

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

Patch: Bluetooth: bnep: reject short frames before parsing [ Upstream
Commit: 0ef2ea86c82b2615902d085cd5a586fe9f58994f
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0ef2ea86c82b2615902d085cd5a586fe9f58994f

Changed files:
  net/bluetooth/bnep/core.c
  kernel/workqueue.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=0ef2ea86c82b2615902d085cd5a586fe9f58994f

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

The original Linux kernel CVE announcement for CVE-2026-53253 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53253

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:L/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:L/I:N/A:H
  The Best / paranoid CVSS score: 7.1

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).