[CVE-2026-74275][MODERATE 7.0] cxl/region: Fix out-of-bounds access in cxl_cancel_auto_attach() [ Upstream

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

CVE: CVE-2026-74275
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: cxl/region: Fix out-of-bounds access in cxl_cancel_auto_attach() [ Upstream
Commit: 44b2397eb67b7f728640989a22d062e41f94ab64
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=44b2397eb67b7f728640989a22d062e41f94ab64
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74275
Analysis date: Sun, 16 Aug 2026 05:31:17 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum**:: actionable Moderate for automation. Strong Important candidate only if a lower-privileged local actor or firmware-controlled CXL topology can reliably influence the failing auto-attach path.
Manual review required: YES

Summary:
A negative `cxled->pos` from failed CXL interleave position calculation can be used as an index into `p->targets[]` during auto-attach cleanup, causing out-of-bounds kernel access and a constrained metadata corruption or crash risk in local CXL device-management paths.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-74275 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74275

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-2026-74275	MODERATE	CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';CWE-129;CWE-125;*CWE-787;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'cxl_cancel_auto_attach can use cxled pos as an index into p targets even when cxled pos contains a negative errno from cxl_region_sort_targets after cxl_calc_interleave_pos fails. This creates an out-of-bounds access in the CXL region auto attach cleanup path and may lead to a kernel crash or memory corruption if adjacent memory is read or later overwritten through the stale position. For the CVSS the PR:L is used for the paranoid score because a reduced capability local management context or service account that can influence CXL region auto assembly may be sufficient in some deployments, although normal CXL configuration is usually administrator controlled. The issue is not network reachable and requires local CXL management or device enumeration conditions. Impact is at least local denial of service and in the worst defensible case may affect confidentiality and integrity due to kernel memory corruption.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 5)  SKIP CVE-2026-74275 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: 87805c32e6ad7b5ce2d9f7f47e76081857a4a335 YES  NO NO unknown 	MAYBE	OOB DANGER INIT UAF HARDWARE  DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=5
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: 4
* Paranoid score: 5
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**:: actionable Moderate for automation. Strong Important candidate only if a lower-privileged local actor or firmware-controlled CXL topology can reliably influence the failing auto-attach path.

## 2. Signal breakdown

Conservative signals:

* Firmware-mediated external influence: +1. CXL region auto-assembly depends on CXL device topology and interleave position calculation, which may be influenced by platform firmware or device configuration rather than ordinary remote input.
* Memory corruption, weak/indirect corruption candidate: +1. A negative `cxled->pos` is used as an index into `p->targets[]`, creating an out-of-bounds access.
* Constrained kernel metadata overwrite candidate: +1. If the earlier out-of-bounds lookup causes the device search to match, the old code can later execute `p->targets[pos] = NULL` with the same negative index. The written value is fixed and not attacker-chosen.
* Integrity impact plausible: +1. The possible negative-index NULL store can corrupt adjacent kernel bookkeeping in the CXL region structure.
* Availability impact realistic: +1. Out-of-bounds kernel access in a region cleanup path can plausibly crash the kernel or corrupt CXL region state.
* Requires admin/root/device-management privileges in typical deployments: -2. Normal CXL region creation, auto-assembly control, and device management are administrator-controlled.

Conservative total: 4

Paranoid additions and adjustments:

* Local lower-privileged trigger concern: +1. In some deployments, CXL management may be delegated to a service account, reduced-capability root, or privileged container-like management context rather than full host root.
* Weak LPE concern: +1. The bug has a plausible corruption sink through negative-index access and a constrained write, but no demonstrated reclaim, arbitrary write, type confusion, or controlled payload.
* Hard or configuration-specific trigger: -1. Triggering depends on CXL auto-attach state and failure of `cxl_calc_interleave_pos()`.
* Constrained/no attacker-controlled payload: -1. The observed write is a fixed NULL into a location derived from a negative errno-like index.

Paranoid total: 5

## 3. Reachability analysis

The bug is local or firmware/device-management mediated, not network reachable. A typical attacker would need the ability to influence CXL region auto-assembly, CXL endpoint decoder state, or platform/device configuration that causes `cxl_calc_interleave_pos()` to fail and leaves `cxled->pos` negative.

In standard deployments this is usually an administrator-controlled path, so the conservative interpretation applies the privilege penalty. However, CXL is a trusted device-management subsystem and some environments may delegate management to orchestration services or reduced-capability local contexts. That supports the paranoid PR:L-style interpretation, but not PR:N.

Namespaces do not normally make CXL management unprivileged. This is also not a default broad local user API like syscalls, io_uring, AF_ALG, or unprivileged netlink.

Call-site confidence: high. The patch shows both the bad lookup path and the later cleanup write path.

## 4. Severity interpretation

This is not an ordinary low-risk correctness fix because the patch removes a negative-index access into a kernel pointer array and changes cleanup logic to scan valid targets instead. The realistic impact is most likely local DoS or CXL region state corruption under uncommon device-management conditions.

Theoretical memory corruption potential exists because the old code can read before `p->targets[]` and may later write `NULL` through the same invalid index. However, the primitive is constrained: the write value is fixed, the target selection is limited by the negative position, and there is no demonstrated attacker-controlled payload, reclaim, callback control, or arbitrary write. Therefore it is best treated as actionable Moderate, with manual review required to decide whether a product-specific CXL deployment makes it Important.

## 5. One-sentence report phrase

A negative `cxled->pos` from failed CXL interleave position calculation can be used as an index into `p->targets[]` during auto-attach cleanup, causing out-of-bounds kernel access and a constrained metadata corruption or crash risk in local CXL device-management paths.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: this is an out-of-bounds kernel access in a trusted CXL region-management path with a plausible constrained write, and the practical severity depends heavily on whether CXL auto-assembly can be influenced by firmware, hotplug, orchestration, or reduced-privilege local management in the evaluated environment.

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

Patch: cxl/region: Fix out-of-bounds access in cxl_cancel_auto_attach() [ Upstream
Commit: 44b2397eb67b7f728640989a22d062e41f94ab64
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=44b2397eb67b7f728640989a22d062e41f94ab64

Changed files:
  drivers/cxl/core/region.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=44b2397eb67b7f728640989a22d062e41f94ab64

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

The original Linux kernel CVE announcement for CVE-2026-74275 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74275

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