[CVE-2026-45962][MODERATE 7.0] ublk: Validate SQE128 flag before accessing the cmd [ Upstream

[CVE-2026-45962][MODERATE 7.0] ublk: Validate SQE128 flag before accessing the cmd [ Upstream

[AL-KERNEL]

CVE: CVE-2026-45962
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: ublk: Validate SQE128 flag before accessing the cmd [ Upstream
Commit: 4b4dff498f46e9802f71bc84258bf73065f51c6a
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4b4dff498f46e9802f71bc84258bf73065f51c6a
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45962
Analysis date: Wed, 27 May 2026 19:13:41 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate at minimum
Manual review required: NO

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-45962 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45962

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: NO

A detailed explanation of the methodology and priority rules is included
at the end of this message.

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

CVE-2026-45962	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:L/I:N/A:H';CWE-125;CWE-126;*CWE-20;CWE-754;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '6.1';DESCR 'ublk_ctrl_uring_cmd() could dump ublk control command fields before verifying that the io_uring request used SQE128. A local user with access to the ublk io_uring control path could submit a non SQE128 command and make the driver read command fields beyond the valid SQE payload. For the CVSS the PR:L is used because triggering requires local access to the ublk control interface, not full administrator privileges in delegated ublk setups. The issue is not network reachable. Impact is primarily denial of service through an out of bounds read or fault, with limited confidentiality concern only if the read values become observable through debug output.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5) 	MAYBE	OOB SIMPLEFIX IMPROVEONLY IO_URING KPANIC  KPANIC LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS 	-	-	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
* Local unprivileged trigger: +1. A local user with access to the ublk io_uring control path can submit a command without `IO_URING_F_SQE128`.
* Local high-control kernel API: +1. The issue is in the ublk plus io_uring control interface.
* Weak memory corruption / OOB read candidate: +1. The bug can read beyond the valid SQE command payload, but no write primitive is shown.
* Reliable kernel crash / DoS: +1. Out-of-bounds access may fault or trigger KASAN/Oops.
* Availability impact realistic: +1. The likely impact is local DoS.
* Paranoid confidentiality concern: +1. Values read by `ublk_ctrl_cmd_dump()` might become observable through debug output or tracing, but this is not a strong leak primitive.
* No arbitrary write or UAF. No direct privilege escalation is demonstrated.

3. Reachability analysis
The bug is reachable locally through ublk io_uring commands. It is not network reachable. Access depends on ublk control permissions and whether unprivileged or delegated ublk use is enabled. Containers matter if they are allowed to use ublk/io_uring against the host kernel. Exploitation is straightforward once the interface is reachable because the missing SQE128 flag is attacker-controlled.

4. Severity interpretation
This is more than a trivial validation bug because it is an OOB read in a high-control io_uring-backed block interface. However, it is not a strong Important candidate because there is no OOB write, UAF, controlled corruption, or proven information leak. It fits Actionable Moderate in paranoid triage and borderline in conservative triage.

5. One-sentence report phrase
ublk can read beyond the valid io_uring SQE command payload by dumping control fields before validating `IO_URING_F_SQE128`, causing local DoS and limited OOB-read concern.

6. Manual review recommendation
MANUAL CHECK RECOMMENDED. The bug affects a local high-control ublk/io_uring path and includes an OOB read, but no write primitive or LPE is shown.

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

Patch: ublk: Validate SQE128 flag before accessing the cmd [ Upstream
Commit: 4b4dff498f46e9802f71bc84258bf73065f51c6a
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4b4dff498f46e9802f71bc84258bf73065f51c6a

Changed files:
  drivers/block/ublk_drv.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=4b4dff498f46e9802f71bc84258bf73065f51c6a

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

The original Linux kernel CVE announcement for CVE-2026-45962 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45962

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:N/I:N/A:H
  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: 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).