[CVE-2026-74712][MODERATE 7.0] vdpa/mlx5: Fix buffer length in create_direct_keys() [ Upstream

[CVE-2026-74712][MODERATE 7.0] vdpa/mlx5: Fix buffer length in create_direct_keys() [ Upstream

[AL-KERNEL]

CVE: CVE-2026-74712
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: vdpa/mlx5: Fix buffer length in create_direct_keys() [ Upstream
Commit: ec3bb289cf19d526224117d5d450a5fd9cbd5ab2
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ec3bb289cf19d526224117d5d450a5fd9cbd5ab2
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74712
Analysis date: Sat, 22 Aug 2026 12:37:17 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A bounded slab out-of-bounds read in mlx5 vDPA create_direct_keys can cause cmd_exec to copy bytes past the allocated command buffer, exposing limited kernel heap data to the device command path and potentially crashing hardened kernels.

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

The original Linux kernel CVE announcement for CVE-2026-74712 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74712

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.

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

CVE-2026-74712	MODERATE	CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:H';CWE-126;CWE-125;CWE-131;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:L';BEST CVSS score: '6.1';DESCR 'A slab out of bounds read occurs in the mlx5 vdpa create_direct_keys path because cmds in points to the in field while cmds inlen was calculated as the size of the whole mlx5_create_mkey_mem object. This makes cmd_exec and mlx5_copy_to_msg read past the allocated command buffer when copying data for the device command. For the CVSS the PR:L is selected because triggering normally requires a local process or service account such as qemu with access to the mlx5 vdpa device setup path, not full host administrator privileges. The issue is not directly network reachable and depends on mlx5 vdpa hardware and virtualization configuration. Impact is at least local denial of service via KASAN report or kernel crash, with limited confidentiality risk because adjacent kernel heap bytes may be copied into the device command path. No direct arbitrary write primitive is shown, so integrity impact is not raised in the base score.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5)  SKIP CVE-2026-74712 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES  NO NO unknown 	MAYBE	READ KASAN OOB LINUS  INCREASED_TO_MODERATE7_FROM_MODERATE_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP	-	-	checked

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

ActionableScore=5
ActionableScoreLower=4

## 1. ActionableScore

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

## 2. Signal breakdown

Conservative signals:

* Local lower-privileged trigger: +1. The observed task is qemu-system and the path is reachable through mlx5 vDPA device setup, so this is more like a local service account or delegated virtualization user than full host root.
* Memory layout invariant restoration: +1. The patch restores consistency between the command input pointer and the input length by subtracting offsetof(struct mlx5_create_mkey_mem, in).
* Privileged kernel/device-management memory corruption path: +1. The bug occurs in mlx5_vdPA MKEY creation and mlx5 command execution, a trusted device-management path.
* Confidentiality impact plausible: +1. The issue is an out-of-bounds read beyond a slab allocation, and adjacent kernel heap bytes may be copied into the device command path.
* Availability impact realistic: +1. KASAN reports a slab-out-of-bounds read, and affected debug or hardened configurations may convert this into a kernel crash.
* Rare and configuration-dependent subsystem: -1. Exploitation depends on mlx5 hardware, vDPA enablement, and a virtualization configuration using this path.

Paranoid additional signal:

* Reliable kernel crash / strong DoS: +1. The CI report shows a concrete KASAN BUG in cmd_exec, so for triage it is reasonable to treat this as a stronger DoS candidate in hardened or panic-on-detection environments.

Not awarded:

* Remote reachable: +0. No realistic network trigger is shown.
* Strong LPE plausibility: +0. No write primitive, UAF reclaim, type confusion, callback control, refcount takeover, or arbitrary write is shown.
* Generic strong memory corruption: +0. This is a bounded read-only OOB, not an OOB write or heap overwrite.
* Integrity impact: +0. The patch does not show attacker-controlled writes or corruption of externally owned data.

## 3. Reachability analysis

The likely trigger is a local process that can exercise mlx5 vDPA setup, such as qemu or a virtualization management component with access to the vDPA device. This is not normally reachable by an arbitrary remote attacker and is not part of a common packet-processing path.

Namespaces or containers may matter if vDPA device access is delegated to a reduced-privilege container or service account. In that case PR:L is more appropriate than PR:H for practical triage. In a locked-down host where only full administrators can configure mlx5 vDPA, the practical risk is lower.

Call-site confidence: high. The commit includes the failing stack through cmd_exec, mlx5_cmd_exec_cb, mlx5_vdpa_exec_async_cmds, and create_direct_keys.

## 4. Severity interpretation

This behaves like an Actionable Moderate issue, not an ordinary low-risk cleanup. The primitive is a real slab out-of-bounds read in a device command construction path, with plausible limited confidentiality exposure and crash potential.

It is not a strong Important candidate by default because the patch supports only a read past the end of an allocation. There is no demonstrated write primitive, lifetime corruption, object replacement, or privilege escalation path.

## 5. One-sentence report phrase

A bounded slab out-of-bounds read in mlx5 vDPA create_direct_keys can cause cmd_exec to copy bytes past the allocated command buffer, exposing limited kernel heap data to the device command path and potentially crashing hardened kernels.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED. YES REQUIRES MANUAL CHECK.

Reason: this is a concrete kernel slab out-of-bounds read in a virtualization and device-management path with plausible confidentiality and DoS impact, even though no direct LPE primitive is demonstrated.

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

Patch: vdpa/mlx5: Fix buffer length in create_direct_keys() [ Upstream
Commit: ec3bb289cf19d526224117d5d450a5fd9cbd5ab2
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ec3bb289cf19d526224117d5d450a5fd9cbd5ab2

Changed files:
  drivers/vdpa/mlx5/core/mr.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=ec3bb289cf19d526224117d5d450a5fd9cbd5ab2

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

The original Linux kernel CVE announcement for CVE-2026-74712 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74712

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:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:H
  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: 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: NO
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).