[CVE-2026-80662][MODERATE REGULAR] cxl: Fix CXL_HEADERLOG_SIZE to match RAS Capability size [ Upstream

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

CVE: CVE-2026-80662
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: cxl: Fix CXL_HEADERLOG_SIZE to match RAS Capability size [ Upstream
Commit: 6fc1919a6f2ed541484dd1f6cd93374044f8fd3d
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6fc1919a6f2ed541484dd1f6cd93374044f8fd3d
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80662
Analysis date: Fri, 28 Aug 2026 04:38:02 -0400
ActionableScore: 4
ActionableScore lower bound: 3
Actionable bucket: Borderline. Manual review recommended
Manual review required: YES

Summary:
A CXL RAS header log size mismatch can cause the kernel to copy about 448 bytes past a valid 64 byte stack embedded header log into a trace event, exposing kernel stack data to userspace readers of trace data.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-80662 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80662

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-2026-80662	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:N/A:L';CWE-125;CWE-126;*CWE-200;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N';BEST CVSS score: '5.3';DESCR 'A CXL RAS header log size mismatch can make the kernel copy 512 bytes where only 64 bytes of real header log data exist. In the CPER path the source header_log is embedded in a stack local structure, so the trace event memcpy can read about 448 bytes past the valid field and place kernel stack data into the trace ring buffer. For the CVSS the PR:L is used because exploitation requires local access to tracefs or another local consumer of trace data, not full kernel code execution. The issue is not network reachable and normally requires a CXL RAS or CPER error event plus trace data access. Impact is primarily information disclosure through kernel stack exposure, with possible low availability concern from out of range MMIO reads. No direct privilege escalation primitive is proven, but the stack disclosure is concrete and should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline. Manual review recommended (with actual score 4)  SKIP CVE-2026-80662 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	DANGER INIT ERRORPATH LOG HARDWARE  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	-	-	checked

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

ActionableScore=4
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 4
* Final recommended bucket: **Borderline. Manual review recommended**::

## 2. Signal breakdown

Triggered signals:

* Firmware-mediated external influence: +1
  The vulnerable path depends on CXL RAS or CPER error reporting, which can be influenced by CXL hardware or firmware error conditions rather than ordinary local syscalls alone.

* Confidentiality impact plausible: +1
  The commit explicitly describes a 512 byte trace event memcpy from a source where only 64 bytes are valid, causing about 448 bytes of kernel stack data to be copied into the trace ring buffer.

* Practical exploit chain demonstrated or strongly implied: +1
  The chain is concrete: oversized header log size -> stack overread in CPER caller -> trace event ring buffer -> userspace readable via tracefs or tracing consumer.

Paranoid-only signal:

* Privileged kernel device management disclosure path: +1
  This is not a strong memory corruption primitive, but the bug is in trusted CXL RAS error handling and exposes kernel stack bytes through a kernel tracing ABI. This justifies manual review sensitivity.

Not awarded:

* Remote reachable: +0
  No realistic direct network trigger is shown.

* Local unprivileged trigger: +0
  Reading tracefs and reliably triggering CXL RAS or CPER events is not generally available to an arbitrary unprivileged user.

* Generic memory corruption: +0
  This is an out-of-bounds read and stack disclosure, not OOB write, UAF, double free, or type confusion.

* Strong DoS: +0
  The MMIO overread may be undesirable, but the primary demonstrated impact is information disclosure, not a reliable crash.

Possible reductions considered:

* Rare hardware condition: not applied in the main score
  CXL hardware is configuration dependent, but the bug exposes real kernel stack data through a standard tracing path when the subsystem is present. Applying a full rare-hardware penalty would likely understate triage value.

Call-site confidence: high.
The relevant copy paths and trace event layout are included in the supplied patch.

## 3. Reachability analysis

The issue is reachable when the system has CXL RAS or CPER error handling active and an uncorrectable CXL protocol error is traced. The attacker needs access to trace output or to a local tracing consumer such as tracefs or a daemon that reads these events.

In typical deployments, tracefs access is restricted to root or tracing-privileged users, so this is not a default unprivileged local trigger. Containers do not normally gain this access unless tracing interfaces are delegated or exposed by the host. The trigger is not network reachable. A malicious or faulty device or firmware could help produce the error event, but that is better modeled as firmware-mediated influence rather than remote reachability.

## 4. Severity interpretation

This behaves like an actionable information disclosure issue, not an ordinary low-risk cleanup. The patch fixes a concrete out-of-bounds read where kernel stack bytes can be copied into a userspace-observable trace buffer.

Realistic exploitation evidence supports confidentiality impact, mainly kernel stack disclosure. It does not support arbitrary write, UAF, type confusion, direct privilege escalation, or remote exploitation. The paranoid score is higher only because stack disclosure can assist later exploitation and because the leak path is concrete enough to deserve manual review.

## 5. One-sentence report phrase

A CXL RAS header log size mismatch can cause the kernel to copy about 448 bytes past a valid 64 byte stack embedded header log into a trace event, exposing kernel stack data to userspace readers of trace data.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED. YES REQUIRES MANUAL CHECK.

Reason: this is a concrete kernel stack information disclosure through trace events, even though exploitation depends on CXL error generation and tracefs or tracing-consumer access.

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

Patch: cxl: Fix CXL_HEADERLOG_SIZE to match RAS Capability size [ Upstream
Commit: 6fc1919a6f2ed541484dd1f6cd93374044f8fd3d
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6fc1919a6f2ed541484dd1f6cd93374044f8fd3d

Changed files:
  drivers/cxl/core/ras.c
  drivers/cxl/core/trace.h
  drivers/cxl/cxl.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=6fc1919a6f2ed541484dd1f6cd93374044f8fd3d

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

The original Linux kernel CVE announcement for CVE-2026-80662 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80662

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:N/A:N
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:L
  The Best / paranoid CVSS score: 5.3

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).