[CVE-2026-93096][MODERATE REGULAR] cxl/features: Serialize multi-part Get/Set Feature transfers [ Upstream

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

CVE: CVE-2026-93096
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: cxl/features: Serialize multi-part Get/Set Feature transfers [ Upstream
Commit: 7682b617db1f19bc606b5f1badadcf1e63a87b14
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7682b617db1f19bc606b5f1badadcf1e63a87b14
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93096
Analysis date: Fri, 18 Sep 2026 03:49:55 -0400
ActionableScore: 4
ActionableScore lower bound: 3
Actionable bucket: Borderline / manual review recommended
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-93096 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93096

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 REGULAR
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-2026-93096	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-93096 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:L/I:H/A:H';CWE-362;CWE-667;CWE-662;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:L';BEST CVSS score: '6.5';DESCR 'Concurrent CXL Get/Set Feature transfers can interleave because the existing mailbox mutex only serializes individual mailbox commands and is released between fragments of a larger transfer. This can corrupt the devices feature transfer context when fwctl RPCs or EDAC scrub ECS repair paths issue overlapping requests to the same mailbox. For the CVSS the PR:L is used because triggering requires local access to a CXL management path such as fwctl or a process context able to drive these operations, but not necessarily full host administrator control in delegated device management deployments. The issue is not network reachable and is triggered through local control plane operations rather than packet traffic. Impact is at least incorrect feature transfer behavior and availability degradation. In the paranoid interpretation, integrity and availability can be high if corrupted feature state affects CXL memory device operation or repair behavior.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 4)  SKIP CVE-2026-93096 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES  NO NO unknown 	MAYBE	INIT SIMPLEFIX HARDWARE 	-	-	checked

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

ActionableScore=4
ActionableScoreLower=3
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: 3
* Conservative score: 3. No floor or cap applied.
* Raw paranoid score: 4
* Paranoid score: 4. No floor or cap applied.
* Final recommended bucket: **Borderline / manual review recommended**::

2. Signal breakdown

Conservative signals:

* +1 Weak / indirect corruption candidate. Multi-part CXL Get/Set Feature transfers can interleave and corrupt the device mailbox feature transfer context.
* +1 Integrity plausible. Interleaving Get/Set Feature fragments may cause incorrect feature data or feature state to be applied or observed on the same CXL mailbox.
* +1 Availability plausible. Corrupted feature transfer context can affect CXL feature handling and EDAC scrub/ECS/repair paths, causing device-management malfunction or memory-device reliability degradation.
* 0 No remote reachability. This is local control-plane access through fwctl or internal EDAC paths, not packet-triggered network input.
* 0 No host-admin penalty. Host-admin-equivalent privilege is not positively established from the supplied evidence.
* 0 No hard race penalty. The bug is a race, but the commit describes ordinary concurrent multi-part transfers rather than a narrow one-shot timing window.

Paranoid additional signal:

* +1 High-value device-management context. The affected paths include CXL memory-device feature control and EDAC scrub/ECS/repair operations, so unresolved device integrity or availability impact deserves manual review.

Important non-awarded signals:

* Controlled reclaim not demonstrated.
* Kernel UAF not demonstrated.
* Arbitrary write not demonstrated.
* Kernel memory corruption not demonstrated.
* Confidentiality impact not awarded because no disclosure path is established.
* Strong LPE or privilege escalation not awarded.
* Remote reachability not established.
* Extra crash/DoS point not awarded because a host kernel crash is not demonstrated.
* CLASS_A not used because the primitive is device transfer context corruption, not controlled kernel corruption or a security-boundary bypass.

3. Reachability analysis

The vulnerable operation is reachable through concurrent CXL feature transfers. The commit explicitly identifies fwctl per-fd RPCs and EDAC scrub/ECS/repair paths as concurrent callers of cxl_get_feature() and cxl_set_feature().

The attacker model is local control-plane access to a CXL management path. The supplied evidence does not prove that an ordinary unprivileged user can open and drive fwctl for the relevant mailbox, but it also does not prove that full host-administrator privilege is required. Therefore HostAdminRequired is UNKNOWN.

No namespace-scoped capability path is shown. NamespaceScopedPrivilege is NO.

No network trigger is shown. The issue is not packet-processing or remotely reachable by default.

A CXL-capable device and feature mailbox support are required. This is hardware-specific, but the supplied evidence does not establish rare physical-only attacker access, so no hardware rarity penalty is applied.

The race is repeatable in principle by issuing overlapping multi-part transfers, especially when payload size exceeds mailbox payload size. The evidence does not show a narrow uncontrollable race.

4. Primitive and severity interpretation

The exact primitive is improper synchronization of multi-part CXL Get/Set Feature mailbox transfers. mbox_mutex protects only individual mailbox commands and is released between fragments, allowing two logical transfers to interleave and corrupt the device transfer context.

This is not a real UAF, not a refcount bug, and not a demonstrated kernel-memory corruption primitive. It is best classified as CLASS_C: invalid active device state / transfer-context corruption without an independently useful kernel exploitation primitive.

The demonstrated consequence is corrupted feature transfer context. The practical impact is likely incorrect feature transfer behavior, failed management operation, or availability degradation of CXL feature handling and EDAC repair/scrub flows.

The speculative consequence is stronger device integrity or availability impact if corrupted feature context affects CXL memory-device repair, scrub, or feature state. That is why paranoid scoring is one point higher, but not enough for CLASS_A or Strong Important.

ImportantCandidate is NO because no controlled kernel corruption, UAF, boundary bypass, privilege escalation, or demonstrated sensitive resource compromise is established.

AutoDowngradeAllowed is YES because the primitive remains a synchronization bug causing device-context corruption without a concrete Important-grade kernel exploitation primitive. Manual review is still recommended due to CXL memory-device management impact.

5. One-sentence report phrase

Concurrent multi-part CXL Get/Set Feature mailbox transfers can interleave because only individual mailbox commands are serialized, corrupting the device feature transfer context and potentially affecting CXL feature management or EDAC repair behavior.

6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Reason: the issue is not a proven kernel memory corruption or privilege-escalation primitive, but it affects CXL memory-device feature management and EDAC scrub/ECS/repair paths, so device integrity and availability impact should be reviewed before automatic closure.

7. Call-site confidence

Call-site confidence: high

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

Patch: cxl/features: Serialize multi-part Get/Set Feature transfers [ Upstream
Commit: 7682b617db1f19bc606b5f1badadcf1e63a87b14
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7682b617db1f19bc606b5f1badadcf1e63a87b14

Changed files:
  drivers/cxl/core/features.c
  drivers/cxl/core/mbox.c
  include/cxl/mailbox.h

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=7682b617db1f19bc606b5f1badadcf1e63a87b14

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

The original Linux kernel CVE announcement for CVE-2026-93096 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93096

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:L/UI:N/S:U/C:L/I:L/A:L
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:H/A:H
  The Best / paranoid CVSS score: 6.5

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: 4

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 REGULAR

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).