[CVE-2026-45994][MODERATE REGULAR] ibmasm: fix OOB reads in command_file_write due to missing size checks

[CVE-2026-45994][MODERATE REGULAR] ibmasm: fix OOB reads in command_file_write due to missing size checks

[AL-KERNEL]

CVE: CVE-2026-45994
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: ibmasm: fix OOB reads in command_file_write due to missing size checks
Commit: a672682d39dd34e2b5ba4feb436723bed65125ff
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a672682d39dd34e2b5ba4feb436723bed65125ff
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45994
Analysis date: Wed, 27 May 2026 17:41:57 -0400
ActionableScore: 4
ActionableScore lower bound: 2
Actionable bucket: Borderline, manual review recommended
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-45994 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45994

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.

======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-45994	MODERATE	CHECK	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:N/A:L';CWE-125;CWE-126;*CWE-200;*CWE-20;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:L/I:N/A:L';BEST CVSS score: '6.1';DESCR 'ibmasm command_file_write() can accept a short user buffer whose dot command header declares a larger command and data size. Later size and timeout parsing and memcpy_toio() can read beyond the allocated kernel buffer and copy adjacent kernel heap bytes to the service processor MMIO path. For the CVSS the PR:L is used in the paranoid score because access to the ibmasm command file may be delegated to a service or reduced privilege operator, although typical deployments may require administrator level device access. The issue is not network reachable by itself and does not provide a kernel write primitive. Impact is mainly confidentiality exposure of kernel heap data to the service processor side, with possible local DoS if invalid MMIO or malformed command handling fails.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended (with actual score 3)  SKIP CVE-2026-45994  SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	WRITE OOB SIMPLEFIX LEAK LINUS  INCREASED_TO_MODERATE7_FROM_MODERATE_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	-	-	checked

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

ActionableScore=4
ActionableScoreLower=2

1. ActionableScore
* Conservative score: 2
* Paranoid score: 4
* Final recommended bucket: **Borderline, manual review recommended**::

2. Signal breakdown
* Weak memory disclosure primitive: +1. The bug causes OOB reads from a kernel heap buffer, but the read data is copied to the service processor MMIO path rather than directly returned to userspace.
* Confidentiality impact plausible: +1. Adjacent kernel heap bytes may be exposed to the service processor side.
* Availability impact plausible: +1. Malformed command handling or invalid device/MMIO interaction may cause local device-path failure or DoS.
* Privileged kernel/device-management path: +1. The bug is in a trusted device command path interacting with IBM ASM service processor hardware.
* Requires privileged or delegated device access: -1 to -2. Typical access to the ibmasm command file is expected to be administrator-only, but delegated service/operator access is plausible.
* Rare hardware/configuration exposure: -1. This requires ibmasm hardware/driver presence.
* No kernel write primitive. No UAF, arbitrary write, page-cache corruption, or LPE path is shown.

3. Reachability analysis
The trigger is local through `command_file_write()` on the ibmasmfs command file. In typical deployments, access is likely restricted to root or a privileged service, but a reduced-privilege management agent could have delegated access. The issue is not network reachable by itself. Practical confidentiality impact depends on whether the attacker can observe or control the service processor side after kernel heap bytes are copied to MMIO.

4. Severity interpretation
This is not ordinary crash-only Moderate because the patch explicitly describes kernel heap OOB reads and data copied to a device/service-processor channel. However, it is not a clear Important candidate because the leak is not directly returned to userspace and exploitation depends on specialized IBM ASM hardware and permissions. It fits borderline/manual-review territory.

5. One-sentence report phrase
`ibmasm` command handling can trust user-controlled dot-command length fields, causing OOB kernel heap reads that may copy adjacent kernel data to the service processor MMIO path.

6. Manual review recommendation
MANUAL CHECK RECOMMENDED. The bug has a real kernel heap OOB-read component, but practical severity depends on ibmasm command-file permissions and whether the service processor side is observable by the attacker.

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

Patch: ibmasm: fix OOB reads in command_file_write due to missing size checks
Commit: a672682d39dd34e2b5ba4feb436723bed65125ff
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a672682d39dd34e2b5ba4feb436723bed65125ff

Commit description:

The command_file_write() handler allocates a kernel buffer of exactly
count bytes and copies user data into it, but does not validate the
buffer against the dot command protocol before passing it to
get_dot_command_size() and get_dot_command_timeout().

Since both the allocation size (count) and the header fields (command_size,
data_size) are independently user-controlled, an attacker can cause
get_dot_command_size() to return a value exceeding the allocation,
triggering OOB reads in get_dot_command_timeout() and an out-of-bounds
memcpy_toio() that leaks kernel heap memory to the service processor.

Fix with two guards: reject writes smaller than sizeof(struct
dot_command_header) before allocation, then after copying user data
reject commands where the buffer is smaller than the total size declared
by the header (sizeof(header) + command_size + data_size). This ensures
all subsequent header and payload field accesses stay within the buffer.

Fixes: 1da177e ("Linux-2.6.12-rc2")
Reported-by: Yuhao Jiang <danisjiang@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Tyllis Xu <LivelyCarpet87@gmail.com>
Link: https://patch.msgid.link/20260314165355.548119-1-LivelyCarpet87@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/misc/ibmasm/ibmasmfs.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=a672682d39dd34e2b5ba4feb436723bed65125ff

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

The original Linux kernel CVE announcement for CVE-2026-45994 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45994

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:H/UI:N/S:U/C:L/I:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:L
  The Best / paranoid CVSS score: 6.1

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: 2
  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).