[CVE-2026-72106][MODERATE 7.0] dm-ioctl: fix a possible overflow in list_version_get_info

[AL-KERNEL <alkernel@kernelcve.org>]

CVE: CVE-2026-72106
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: dm-ioctl: fix a possible overflow in list_version_get_info
Commit: 29536a9ff146d9bbd618959857ed2e691cda1d21
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=29536a9ff146d9bbd618959857ed2e691cda1d21
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72106
Analysis date: Sat, 15 Aug 2026 04:39:28 -0400
ActionableScore: 5
ActionableScore lower bound: 3
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A bounds check bug in dm-ioctl list_version_get_info can allow a local caller with access to the device-mapper control ioctl to trigger a small kernel buffer overflow when listing target versions, with realistic DoS impact and limited but nonzero concern for privilege escalation.

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

The original Linux kernel CVE announcement for CVE-2026-72106 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72106

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.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-72106	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:H/I:H/A:H';*CWE-787;CWE-131;CWE-122;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 kernel buffer overflow exists in the device mapper ioctl path because list_version_get_info checks space using sizeof(tt version), which covers only 12 bytes, while the code can write the full dm_target_versions header of 16 bytes plus the target name. A local caller that can issue the affected device mapper ioctl may be able to craft an output buffer size that passes the check but causes a small out of bounds write in kernel memory. For the CVSS the PR:L in the paranoid score is used because reduced capability administrators, container root with delegated device mapper access, or service accounts with CAP_SYS_ADMIN over /dev/mapper/control may reach this interface without being full host administrators. The issue is not network reachable and requires local access to the device mapper control interface. Impact is at least local denial of service via kernel memory corruption, and in the worst case may allow confidentiality or integrity impact and privilege escalation, so it should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4)	YES	OOB DISK SIMPLEFIX LINUS  INCREASED_TO_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCORELOWERTHAN6 DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=5
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum**

## 2. Signal breakdown

Paranoid scoring:

* Constrained kernel buffer overwrite: +1
  The bounds check used sizeof(tt->version), 12 bytes, while the later write can emit struct dm_target_versions, 16 bytes, plus the target name.

* Weak LPE concern: +1
  This is a real kernel OOB write, but the overwrite appears small and mostly kernel-derived, with no demonstrated attacker-controlled target or payload.

* Privileged kernel/device-management memory corruption path: +1
  The bug is in the device-mapper ioctl path, a trusted storage management subsystem.

* Important filesystem/storage path: +1
  Device mapper is an important block/storage management component.

* Availability impact realistic: +1
  A kernel heap overwrite in this path can plausibly cause a crash or corrupted kernel state.

* Requires admin/root/CAP_SYS_ADMIN in typical deployments: -1 in paranoid scoring
  Typical access to /dev/mapper/control requires CAP_SYS_ADMIN, but reduced-capability root, container root with delegated device-mapper access, or service accounts may make PR:L a defensible triage assumption.

Conservative scoring applies the full privilege penalty:

* Same positive signals except weak LPE is treated cautiously.
* Requires admin/root/CAP_SYS_ADMIN in typical deployments: -2.
* Conservative result: 3.

Call-site confidence: medium. The patch shows the faulty size check and the commit message explicitly describes the 12 byte vs 16 byte write mismatch, but the full ioctl allocation and copyout call path is not included in the provided diff.

## 3. Reachability analysis

The bug is locally reachable through the device-mapper ioctl interface, typically /dev/mapper/control. In normal deployments this requires CAP_SYS_ADMIN or equivalent administrative device-management privileges, so it is not a plain unprivileged local bug. Namespaces or containers may matter if device-mapper access is delegated to container root or a reduced-privilege service account, in which case the practical privilege level can be closer to PR:L than PR:H. The issue is not network reachable.

## 4. Severity interpretation

This is stronger than an ordinary Moderate correctness bug because the patch fixes a concrete kernel buffer overflow. It is not enough to claim a strong LPE primitive from the diff alone because the overflow appears small, the written values are not clearly attacker-controlled, and no reclaim, object replacement, arbitrary write, or type confusion primitive is shown. Realistically it is at least a local privileged kernel memory corruption and DoS concern. Paranoid triage should keep it as Actionable Moderate because kernel OOB writes in storage management paths can be underestimated.

## 5. One-sentence report phrase

A bounds check bug in dm-ioctl list_version_get_info can allow a local caller with access to the device-mapper control ioctl to trigger a small kernel buffer overflow when listing target versions, with realistic DoS impact and limited but nonzero concern for privilege escalation.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED.

Reason: this is a concrete kernel OOB write in a storage management ioctl path, and although the primitive appears constrained, it should not be auto-closed without checking allocator context, object adjacency, and whether delegated device-mapper access exists in the target environment.

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

Patch: dm-ioctl: fix a possible overflow in list_version_get_info
Commit: 29536a9ff146d9bbd618959857ed2e691cda1d21
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=29536a9ff146d9bbd618959857ed2e691cda1d21

Commit description:

sizeof(tt->version) is 12 bytes, but the code writes 16 bytes into the
output buffer - info->vers->version[0], info->vers->version[1],
info->vers->version[2] and info->vers->next. This can cause buffer
overflow.

Fix this buffer overflow by replacing "sizeof(tt->version)" with
"sizeof(struct dm_target_versions)".

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Assisted-by: Claude:claude-opus-4.6
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/md/dm-ioctl.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=29536a9ff146d9bbd618959857ed2e691cda1d21

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

The original Linux kernel CVE announcement for CVE-2026-72106 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72106

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: 3
  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).