[CVE-2026-68125][MODERATE 7.0] mac802154: llsec: reject frames shorter than the authentication tag

[CVE-2026-68125][MODERATE 7.0] mac802154: llsec: reject frames shorter than the authentication tag

[AL-KERNEL]

CVE: CVE-2026-68125
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: mac802154: llsec: reject frames shorter than the authentication tag
Commit: 5bbf0cd9b6a7076af86c75e87e180099be2e11ae
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5bbf0cd9b6a7076af86c75e87e180099be2e11ae
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68125
Analysis date: Mon, 10 Aug 2026 09:51:58 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A malformed secured IEEE 802.15.4 frame with payload shorter than the authentication tag can trigger an integer underflow in mac802154 LLSEC AEAD handling, causing out-of-bounds scatterlist traversal and a kernel crash from an adjacent radio attacker.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-68125 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68125

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-2026-68125	MODERATE	CHECK WITH IMPACT FROM ORIG NN LOW	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-191;CWE-125;*CWE-20;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 secured IEEE 802.15.4 frame can reach llsec_do_decrypt_auth with datalen smaller than the authentication tag length. The subtraction datalen - authlen then underflows and is used as an unsigned AEAD associated data length close to 4 GiB, causing crypto_aead_decrypt to walk beyond the real skb backed scatterlist. A remote peer in radio range can trigger this with a malformed secured frame when mac802154 LLSEC processing is enabled, leading to a kernel crash or general protection fault in the AEAD scatterwalk. For the CVSS the PR:N is selected because no local user account or local code execution on the victim is needed beyond adjacent radio reachability to the IEEE 802.15.4 interface. The issue is not Internet routable in the usual sense and is better modeled as AV:A because exploitation requires proximity to the wireless personal area network. Impact is at least denial of service. For the paranoid score, limited confidentiality impact is kept because the bug creates an out of bounds read style scatterlist walk, but integrity impact is not raised without evidence of an out of bounds write or stronger memory corruption primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5)	YES	KASAN LINUS  KPANIC INCREASED_TO_MODERATE_FROM_LOW_BASED_ON_GUESSCVSS	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
  The malformed secured IEEE 802.15.4 frame is attacker-controlled and can be sent by a peer in radio range. This is adjacent-network reachable rather than Internet-routable.

* Memory corruption, weak / indirect corruption candidate: +1
  The bug is an integer underflow in `datalen - authlen` that becomes a very large unsigned AEAD associated-data length. This causes `crypto_aead_decrypt()` to walk beyond the real skb-backed scatterlist. This is an OOB read / invalid scatterlist traversal, not an OOB write.

* Reliable kernel crash / strong DoS: +1
  The commit states that the issue was dynamically reproduced on a KASAN kernel as a general-protection fault in AEAD scatterwalk.

* Availability impact realistic: +1
  A malformed frame can trigger a kernel fault in receive-side LLSEC processing. This is a realistic system availability impact when mac802154 LLSEC is enabled and reachable.

* Rare AND difficult-to-reach subsystem/configuration: -1
  IEEE 802.15.4 LLSEC is not a broad default Internet-facing path. Exploitation requires an IEEE 802.15.4 interface, LLSEC processing, and radio-range access.

* Paranoid confidentiality impact plausible: +1
  The oversized associated-data length causes an out-of-bounds read-style scatterlist walk. There is no demonstrated data disclosure path, so this is only counted in the paranoid score.

No integrity impact or LPE bonus is assigned. The patch does not show an OOB write, UAF reclaim, type confusion, refcount takeover, callback control, or arbitrary write primitive.

## 3. Reachability analysis

The attacker can be any IEEE 802.15.4 peer in radio range that can send a malformed secured frame to the vulnerable interface. No local account or local code execution on the victim is required, so PR:N is reasonable for CVSS-style analysis.

This is not Internet-routable in the usual sense. It should be modeled as adjacent network exposure, similar to AV:A, because the attacker must be near or otherwise able to inject frames into the relevant wireless personal area network.

The path depends on mac802154 LLSEC being enabled and used. That limits broad exposure, but the input is fully attacker-controlled once the radio and LLSEC path are reachable.

## 4. Severity interpretation

This behaves like an actionable Moderate issue, with a paranoid score reaching the lower end of Important-review territory. The realistic demonstrated impact is DoS through kernel crash or general-protection fault.

Theoretical memory-corruption concern exists because the crypto scatterwalk consumes an attacker-induced length far beyond the real frame buffer. However, the evidence supports OOB read / invalid traversal rather than controlled write, privilege escalation, or arbitrary code execution.

Manual review is justified because the issue is network-adjacent, attacker-triggerable, and involves crypto scatterlist traversal with a near-4 GiB derived length.

## 5. One-sentence report phrase

A malformed secured IEEE 802.15.4 frame with payload shorter than the authentication tag can trigger an integer underflow in mac802154 LLSEC AEAD handling, causing out-of-bounds scatterlist traversal and a kernel crash from an adjacent radio attacker.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: adjacent-network attacker input reaches a kernel crypto scatterwalk path with an underflowed length and demonstrated GPF. The realistic impact is DoS, but the OOB read-style primitive and wireless reachability make this unsuitable for automatic closure.

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

Patch: mac802154: llsec: reject frames shorter than the authentication tag
Commit: 5bbf0cd9b6a7076af86c75e87e180099be2e11ae
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5bbf0cd9b6a7076af86c75e87e180099be2e11ae

Commit description:

llsec_do_decrypt_auth() computes the associated-data length for the
AEAD request as

	assoclen += datalen - authlen;

where datalen is the number of bytes after the MAC header and authlen
(4, 8 or 16) is the length of the authentication tag. Nothing verifies
that the frame actually carries at least authlen payload bytes. A
secured frame whose payload is shorter than the tag makes
datalen - authlen negative; assoclen is then passed to
aead_request_set_ad() as an unsigned value close to 4 GiB, so
crypto_aead_decrypt() walks far off the end of the scatterlist that
only spans the real frame.

The frame is fully attacker-controlled and reaches this path from any
IEEE 802.15.4 peer in radio range. Reject frames whose payload is
shorter than the authentication tag before the subtraction.

Dynamically reproduced on a KASAN kernel as a general-protection-fault
in the AEAD scatterwalk, and the fix confirmed.

Fixes: 4c14a2f ("mac802154: add llsec decryption method")
Cc: stable@vger.kernel.org
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Doruk Tan Ozturk <doruk@0sec.ai>
Link: https://patch.msgid.link/20260716193423.32498-1-doruk@0sec.ai
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  net/mac802154/llsec.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=5bbf0cd9b6a7076af86c75e87e180099be2e11ae

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

The original Linux kernel CVE announcement for CVE-2026-68125 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68125

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).