[CVE-2026-80584][MODERATE 7.0] s390/qeth: validate user buffer length in SNMP and ARP query ioctls

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

CVE: CVE-2026-80584
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: s390/qeth: validate user buffer length in SNMP and ARP query ioctls
Commit: 9d00eeb2d27f4cc817c5e408760226d43f811ec6
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9d00eeb2d27f4cc817c5e408760226d43f811ec6
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80584
Analysis date: Wed, 26 Aug 2026 13:09:49 -0400
ActionableScore: 7
ActionableScore lower bound: 4
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A local qeth SNMP or ARP query ioctl can use a too small user supplied buffer length to trigger u32 underflow in reply bounds checking, causing memcpy() past a kernel allocation and possible kernel crash or heap corruption.

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

The original Linux kernel CVE announcement for CVE-2026-80584 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80584

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-2026-80584	MODERATE	CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H';CWE-191;*CWE-787;CWE-122;*CWE-20;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7.8';DESCR 'A kernel heap out of bounds write is possible in the s390 qeth SNMP and ARP query ioctl paths because qeth_snmp_command() and qeth_l3_arp_query() accept a user supplied udata_len that can be smaller than the fixed reply offset. The later bounds check subtracts udata_offset from udata_len using u32 arithmetic, so a too small length can underflow and make the check pass before memcpy writes past the allocated buffer. For the CVSS the PR:L is used because a local user or process can reach the ioctl interface in plausible deployments, while full administrator privileges are not clearly required by the bug class. The issue is not directly network reachable because the trigger is a local ioctl rather than packet traffic. Impact is at least a local denial of service via kernel crash and in the paranoid case may allow confidentiality and integrity impact due to kernel heap memory corruption.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 6)	YES	OOB SIMPLEFIX NETWORK HARDWARE LINUS KPANIC  KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFDH	NO	NO	checked

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

ActionableScore=7
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: 4
* Paranoid score: 7
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

* Local unprivileged or low-privileged trigger: +1
  The vulnerable path is reached through local qeth SNMP and ARP query ioctls. Exact permission checks may depend on ioctl path and deployment, but full host-root is not clearly required from the patch context.

* Memory corruption, strong corruption primitive in paranoid scoring: +2
  The commit explicitly describes memcpy() writing past the allocated kernel buffer due to u32 underflow. This is a kernel heap OOB write.

* Constrained kernel buffer overwrite in conservative scoring: +1
  Conservative interpretation treats the overwrite as constrained because the copied data appears to come from driver or adapter reply handling, and the patch does not demonstrate attacker-controlled target selection or payload shaping.

* Weak LPE concern: +1
  Kernel heap OOB write can plausibly become more than DoS, but no concrete reclaim, arbitrary write, object replacement, or privilege escalation chain is shown.

* Reliable kernel crash / strong DoS: +1
  Small or zero udata_len can produce an invalid allocation size or ZERO_SIZE_PTR case, making crash or memory corruption realistic.

* Privileged kernel/device-management memory corruption path: +1
  The corruption occurs in the qeth network driver ioctl handling path, a trusted device-management context.

* Confidentiality impact plausible in paranoid scoring: +1
  Heap corruption can sometimes be turned into limited disclosure, but this is not demonstrated.

* Integrity impact plausible in paranoid scoring: +1
  Heap OOB write gives plausible integrity impact in worst-case triage.

* Rare hardware / difficult exposure: -1
  The affected qeth driver is specific to s390 networking environments and is not broadly present on typical Linux systems.

## 3. Reachability analysis

The trigger is local ioctl access to qeth SNMP or ARP query functionality. It is not directly network-triggerable because packets alone do not invoke the ioctl path. Network or firmware state may influence returned data, but the primary trigger remains local.

Namespaces and containers may matter if qeth device ioctls or network administration capabilities are delegated. If the ioctl is gated by CAP_NET_ADMIN in a given product, the conservative score should be used. If a low-privileged local process can reach the ioctl, the paranoid score is appropriate.

The path is hardware and platform specific. It requires s390 qeth devices and the relevant driver functionality, so exposure is narrower than common networking core bugs.

## 4. Severity interpretation

This is not an ordinary validation-only bug. The patch description explicitly identifies an integer underflow followed by memcpy() past the allocated buffer, which is a concrete kernel heap OOB write.

Realistic exploitation evidence supports at least local DoS and manual review. Practical privilege escalation is not demonstrated, but the memory corruption primitive is strong enough to avoid auto-closing. Conservative handling is borderline manual review, while paranoid handling is a Strong Important candidate.

## 5. One-sentence report phrase

A local qeth SNMP or ARP query ioctl can use a too small user supplied buffer length to trigger u32 underflow in reply bounds checking, causing memcpy() past a kernel allocation and possible kernel crash or heap corruption.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: explicit kernel heap OOB write is present, with possible LPE concern even though exploitability is constrained by s390 qeth hardware and local ioctl reachability.

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

Patch: s390/qeth: validate user buffer length in SNMP and ARP query ioctls
Commit: 9d00eeb2d27f4cc817c5e408760226d43f811ec6
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9d00eeb2d27f4cc817c5e408760226d43f811ec6

Commit description:

qeth_snmp_command() and qeth_l3_arp_query() allocate a buffer sized by
a user-supplied length (udata_len) without checking a lower bound, then
set udata_offset to a fixed non-zero value and pass both to a reply
callback. The callback bounds-checks the copy with

        if ((udata_len - udata_offset) < len)

Both fields are u32, so a udata_len smaller than udata_offset makes the
subtraction wrap and the check pass, and the following memcpy() writes
past the allocation. A udata_len of 0 also yields ZERO_SIZE_PTR from
kzalloc(), which the existing NULL check does not catch.

Reject buffers smaller than udata_offset before allocating, so the
callback subtraction can no longer underflow.

Fixes: 4a71df5 ("qeth: new qeth device driver")
Cc: stable@vger.kernel.org
Reviewed-by: Alexandra Winter <wintera@linux.ibm.com>
Signed-off-by: Hidayath Khan <hidayath@linux.ibm.com>
Reviewed-by: Joe Damato <joe@dama.to>
Link: https://patch.msgid.link/20260730142216.218309-1-hidayath@linux.ibm.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/s390/net/qeth_core_main.c
  drivers/s390/net/qeth_l3_main.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=9d00eeb2d27f4cc817c5e408760226d43f811ec6

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

The original Linux kernel CVE announcement for CVE-2026-80584 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80584

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:L/I:L/A:H
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 7.8

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: 7

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).