[CVE-2026-53124][LOW] ublk: reset per-IO canceled flag on each fetch [ Upstream

[CVE-2026-53124][LOW] ublk: reset per-IO canceled flag on each fetch [ Upstream

[AL-KERNEL]

CVE: CVE-2026-53124
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: ublk: reset per-IO canceled flag on each fetch [ Upstream
Commit: 63335e5a67d89bb7cb9b023bbb3785896587a648
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=63335e5a67d89bb7cb9b023bbb3785896587a648
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53124
Analysis date: Wed, 24 Jun 2026 15:50:14 -0400
ActionableScore: 2
ActionableScore lower bound: 1
Actionable bucket: Ordinary Moderate / Low-like storage DoS
Manual review required: NO

Summary:
A ublk per-IO cancellation state bug can leave fetched commands permanently incomplete if the userspace server dies during recovery, causing local denial of service for the affected ublk device without evidence of memory corruption or privilege escalation.

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

The original Linux kernel CVE announcement for CVE-2026-53124 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53124

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: LOW
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-2026-53124	LOW	CHECK	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';*CWE-664;CWE-404;CWE-755;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'A ublk cancellation state bug can leave outstanding fetch commands permanently incomplete when a ublk server starts device recovery and dies after fetching only a nonempty subset of queue IOs. The per IO canceled flag can remain set even after a fetch command has been submitted, which prevents ublk_cancel_cmd from completing the outstanding io_uring command with io_uring_cmd_done(). This can stall cancellation and recovery for the affected ublk device and can cause denial of service for storage served by that device. For the CVSS the PR:L is used in the paranoid score because ublk can be driven by a local userspace server and some deployments allow reduced capability or unprivileged ublk daemons, even though initial device setup may be administrative. The issue is not network reachable and requires local control over the ublk server or recovery path. Impact is availability only.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like storage DoS (with actual score 2)  SKIP CVE-2026-53124  SKIP The Fixes patch not applied yet, so unlikely that actual: 728cbac5fe219d3b8a21a0688a08f2b7f8aeda2b YES  NO NO unknown 	MAYBE	LOCK SIMPLEFIX HARDWARE IO_URING  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	-	-	checked

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

ActionableScore=2
ActionableScoreLower=1

## 1. ActionableScore

* Conservative score: 1
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate / Low-like storage DoS**

## 2. Signal breakdown

* Reliable device-level DoS / stuck recovery: +1
  The bug can leave outstanding ublk fetch commands permanently incomplete, blocking cancellation and recovery for the affected device.
* Important filesystem/storage path: +1
  ublk is a block-device path, and the impact affects storage served by the userspace block driver.
* Local high-control kernel data-plane API: +1 in paranoid interpretation
  ublk is driven through userspace interaction and io_uring command paths, but the demonstrated issue is state bookkeeping rather than memory corruption.
* Hard or special lifecycle condition required: -1
  Triggering requires recovery, partial fetch completion for a nonempty subset of queue IOs, and server death before all IOs are fetched.
* Requires admin or device-management privileges in typical deployments: -2 conservative
  Creating and managing ublk devices is normally privileged, although some deployments may use reduced-capability or unprivileged ublk daemons.
* Rare or configuration-dependent subsystem: -1 conservative
  ublk is not a default broad-exposure subsystem on most systems.

No generic memory corruption, UAF, double-free, OOB write, page-cache corruption, or security-boundary bypass is supported by the patch.

## 3. Reachability analysis

The bug is local and requires control over a ublk server or its recovery lifecycle. It is not network reachable. In typical deployments, setting up and managing ublk devices requires administrative or device-management privileges, so conservative scoring applies a privilege penalty. In a more paranoid deployment model, an unprivileged or reduced-capability ublk daemon may make the recovery failure path reachable by a less privileged local process, but the impact remains availability-only.

## 4. Severity interpretation

This behaves like an ordinary Moderate or Low-like local storage DoS, not an Important-class kernel vulnerability. The patch fixes stale cancellation state for per-IO bookkeeping and does not indicate memory lifetime corruption or attacker-controlled overwrite. Theoretical impact is a stuck device recovery path. Realistic impact is denial of service for the affected ublk-backed storage, not privilege escalation.

## 5. One-sentence report phrase

A ublk per-IO cancellation state bug can leave fetched commands permanently incomplete if the userspace server dies during recovery, causing local denial of service for the affected ublk device without evidence of memory corruption or privilege escalation.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

This can be auto-closed for urgent-security triage because it is a local, configuration-dependent ublk recovery DoS with no supported memory corruption, confidentiality impact, integrity impact, or privilege-escalation primitive.

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

Patch: ublk: reset per-IO canceled flag on each fetch [ Upstream
Commit: 63335e5a67d89bb7cb9b023bbb3785896587a648
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=63335e5a67d89bb7cb9b023bbb3785896587a648

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=63335e5a67d89bb7cb9b023bbb3785896587a648

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

The original Linux kernel CVE announcement for CVE-2026-53124 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53124

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:H/PR:H/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.7

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: 1
  Paranoid ActionableScore: 2

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: LOW
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): LOW

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).