[CVE-2026-53059][IMPORTANT] dm log: fix out-of-bounds write due to region_count overflow [ Upstream

[CVE-2026-53059][IMPORTANT] dm log: fix out-of-bounds write due to region_count overflow [ Upstream

[AL-KERNEL]

CVE: CVE-2026-53059
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: dm log: fix out-of-bounds write due to region_count overflow [ Upstream
Commit: 44ab8875ae4a2842bde2d756bed195d375e0debb
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=44ab8875ae4a2842bde2d756bed195d375e0debb
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53059
Analysis date: Wed, 24 Jun 2026 13:42:26 -0400
ActionableScore: 8
ActionableScore lower bound: 5
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A device-mapper mirror log region_count truncation can underallocate internal bitsets and allow local privileged or delegated storage-management users to trigger out-of-bounds writes to vmalloc-backed kernel memory, causing a kernel crash and potentially requiring manual review for privilege-escalation risk.

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

The original Linux kernel CVE announcement for CVE-2026-53059 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53059

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: IMPORTANT
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
======================================================================

CVE-2026-53059	IMPORTANT	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:H/A:H';CWE-190;CWE-131;*CWE-787;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7.8';DESCR 'A device-mapper mirror log can underallocate internal bitsets because create_log_context stores the region count in a 32-bit unsigned int while the sector calculation can exceed UINT_MAX. The truncated value is used for allocation sizing, while later log operations can address the full untruncated region space, causing out-of-bounds writes to vmalloc backed kernel memory. For the CVSS the PR:L reflects environments where a local user or delegated service can create device-mapper targets through CAP_SYS_ADMIN or equivalent storage management rights, not necessarily full host root. The issue is not network reachable and requires local control over device-mapper configuration. Impact is at least local denial of service via kernel crash, and because the primitive is an out-of-bounds kernel memory write, worst case impact may include privilege escalation or broader confidentiality and integrity compromise.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 7)	YES	WRITE OOB DANGER DISK KERNEL_PANIC_PLUS_UAF HARDWARE LINUS BOOT KPANIC 	NO	NO	checked

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

ActionableScore=8
ActionableScoreLower=5

## 1. ActionableScore

* Conservative score: 5
* Paranoid score: 8
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative score signals:

* Generic memory corruption: +2. The patch and commit explicitly describe out-of-bounds writes to vmalloc-backed kernel memory due to region_count truncation and underallocated bitsets.
* Reliable kernel crash / strong DoS: +1. The commit provides a concrete crash in core_in_sync and says reboot is needed.
* Important filesystem/storage path: +1. The bug is in device-mapper mirror log handling, a core block/storage subsystem path.
* Privileged kernel/device-management memory corruption path: +1. The corruption occurs in a trusted kernel storage-management subsystem.
* Requires admin/root/CAP_SYS_ADMIN in typical deployments: -2. Creating device-mapper targets normally requires privileged local control.

Paranoid additional signals:

* Privilege escalation plausible: +1. The primitive is an OOB kernel write, but it is bitset-oriented and not clearly an arbitrary write, so this is a weak-to-medium LPE concern rather than a fully demonstrated LPE primitive.
* Confidentiality impact plausible: +1. Kernel memory corruption can theoretically affect sensitive kernel state, but no direct disclosure primitive is shown.
* Integrity impact plausible: +1. OOB writes can corrupt adjacent kernel/vmalloc metadata or objects.
* Availability impact realistic: +1. The demonstrated failure is system-wide and requires reboot.
* Reduced privilege interpretation: penalty weakened from -2 to -1. In some environments, storage-management services, container root with delegated privileges, or constrained CAP_SYS_ADMIN contexts may make this less than full host-root in practical risk terms.

## 3. Reachability analysis

The bug is locally triggerable through device-mapper configuration, specifically by creating a mirror target with a very large length and small region size so that region_count exceeds UINT_MAX. In ordinary deployments this requires root or CAP_SYS_ADMIN and access to the device-mapper control interface, so it is not remotely reachable and not generally available to unprivileged users. Namespaces usually do not make device-mapper safely unprivileged, but delegated storage-management environments can reduce the effective privilege barrier. The path is not a packet or network path, but device-mapper is a broadly deployed storage subsystem.

## 4. Severity interpretation

This is stronger than an ordinary Moderate because the patch describes a concrete integer truncation leading to underallocation and out-of-bounds kernel writes. Realistic exploitation evidence currently points to reliable local kernel crash and reboot-required DoS. Theoretical escalation is plausible because the primitive is kernel memory corruption, but the write appears constrained to bit operations in vmalloc-backed bitsets and no controlled overwrite, reclaim, or object-confusion exploit path is demonstrated. Therefore conservative handling is Actionable Moderate, while paranoid triage should treat it as a Strong Important candidate.

## 5. One-sentence report phrase

A device-mapper mirror log region_count truncation can underallocate internal bitsets and allow local privileged or delegated storage-management users to trigger out-of-bounds writes to vmalloc-backed kernel memory, causing a kernel crash and potentially requiring manual review for privilege-escalation risk.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: this is a concrete OOB kernel write in a core storage subsystem, with demonstrated crash behavior and a plausible but not proven LPE path due to constrained memory corruption.

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

Patch: dm log: fix out-of-bounds write due to region_count overflow [ Upstream
Commit: 44ab8875ae4a2842bde2d756bed195d375e0debb
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=44ab8875ae4a2842bde2d756bed195d375e0debb

Changed files:
  drivers/md/dm-log.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=44ab8875ae4a2842bde2d756bed195d375e0debb

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

The original Linux kernel CVE announcement for CVE-2026-53059 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53059

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: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: 5
  Paranoid ActionableScore: 8

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: IMPORTANT
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): IMPORTANT

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).