[CVE-2026-68274][MODERATE 7.0] drm/xe/guc: Fix buffer overflow in steered register list allocation [ Upstream

[CVE-2026-68274][MODERATE 7.0] drm/xe/guc: Fix buffer overflow in steered register list allocation [ Upstream

[AL-KERNEL]

CVE: CVE-2026-68274
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: drm/xe/guc: Fix buffer overflow in steered register list allocation [ Upstream
Commit: b485bfb45555163bfa5f565d6a3415fcb3035b02
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b485bfb45555163bfa5f565d6a3415fcb3035b02
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68274
Analysis date: Mon, 10 Aug 2026 18:55:48 -0400
ActionableScore: 7
ActionableScore lower bound: 4
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A kernel heap out-of-bounds write in drm xe GuC capture allocation can corrupt adjacent slab objects on affected Xe hardware, causing at least local DoS and requiring manual review for possible LPE impact.

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

The original Linux kernel CVE announcement for CVE-2026-68274 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68274

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
======================================================================

CVE-2026-68274	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-787;CWE-131;CWE-122;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'A kernel heap out-of-bounds write can occur in drm xe GuC capture setup because the steered register extarray is sized only from g_dss_mask while the fill path iterates over the union of g_dss_mask and c_dss_mask. On platforms with compute-only DSS bits, the loop can write past the allocated buffer and corrupt adjacent slab objects, with observed symptoms such as list_del corruption and SLUB redzone overwrites during device unbind. For the CVSS the PR:L is used for the paranoid score because some deployments expose DRM render nodes to local users and a local GPU workload may be able to reach capture or recovery paths, even though driver unbind and module reload are administrative operations. The issue is not network reachable and requires local interaction with the affected GPU driver and hardware topology. Impact is at least local denial of service via kernel crash, and in worst case may allow confidentiality or integrity impact due to kernel slab memory corruption.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 6)  SKIP CVE-2026-68274 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: b170d696c1e2226713471d810c63b1162335079f YES  NO NO unknown 	MAYBE	OOB DANGER HARDWARE KPANIC 	-	-	checked

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

ActionableScore=7
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: 4
* Paranoid score: 7
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Memory corruption, Strong corruption primitive: +2. The patch fixes an allocation size mismatch that leads to an out-of-bounds write past a kernel heap allocation.
* Reliable kernel crash / strong DoS: +1. The commit describes list_del corruption and SLUB redzone overwrites during drm_managed_release on device unbind.
* Privileged kernel/device-management memory corruption path: +1. The corruption occurs inside the DRM Xe GuC device-management path.
* Confidentiality impact plausible: +1. Conservative impact is limited but possible because this is slab memory corruption.
* Integrity impact plausible: +1. Adjacent slab objects can be overwritten.
* Availability impact realistic: +1. A kernel crash is directly supported by the observed corruption symptoms.
* Requires admin/root/CAP_* in typical deployments: -2. The most explicit trigger in the report is device unbind, which is normally administrative.
* Corruption primitive highly constrained or metadata-only: -1. The overflow data is likely kernel-derived steered register list data rather than a fully attacker-controlled payload.
* Hard or hardware-specific condition: -1. The bug requires affected Xe hardware topology with compute-only DSS bits.

Paranoid additional interpretation:

* Local unprivileged trigger: +1. Some systems expose DRM render nodes to local users, and a local GPU workload may plausibly reach GuC capture or recovery paths.
* Privilege escalation plausible: +1. This is not a demonstrated LPE primitive, but slab OOB write into adjacent kernel objects is enough for weak LPE concern and manual review.
* Do not add remote reachability. This is not network-triggerable.

## 3. Reachability analysis

The issue is local and hardware dependent. The direct observed failure occurs during device unbind and drm_managed_release, which normally requires administrative privileges. However, the vulnerable allocation and fill logic is in the Xe GuC capture path, and DRM render nodes are commonly accessible to local users on desktop or GPU compute systems. That makes PR:L defensible for the paranoid score if local GPU workloads can trigger GuC capture, reset, error capture, or recovery behavior.

Namespaces and containers do not automatically make this reachable, but GPU device passthrough or exposed render nodes can reduce practical privilege requirements. The path is not network reachable. Realistic exploitation requires an affected Intel Xe platform with compute-only DSS bits and a way to exercise the GuC capture list allocation and release path.

Call-site confidence: medium. The patch and commit describe the allocation mismatch and observed slab corruption, but the full set of runtime call paths that can trigger GuC capture is not included in the supplied diff.

## 4. Severity interpretation

This is not an ordinary Moderate cleanup bug. The patch fixes a real kernel heap out-of-bounds write with observed slab corruption. Conservative handling can treat it as local privileged DoS with constrained corruption, but paranoid triage should keep it in an Important-candidate bucket because adjacent slab object corruption can sometimes become exploitable depending on object layout and trigger control.

Theoretical memory corruption potential is strong because this is an OOB write. Realistic exploitation evidence is weaker because attacker control over payload, target object, and trigger reliability is not demonstrated.

## 5. One-sentence report phrase

A kernel heap out-of-bounds write in drm xe GuC capture allocation can corrupt adjacent slab objects on affected Xe hardware, causing at least local DoS and requiring manual review for possible LPE impact.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: this is confirmed kernel heap memory corruption with SLUB redzone overwrite and list corruption symptoms. YES REQUIRES MANUAL CHECK.

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

Patch: drm/xe/guc: Fix buffer overflow in steered register list allocation [ Upstream
Commit: b485bfb45555163bfa5f565d6a3415fcb3035b02
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b485bfb45555163bfa5f565d6a3415fcb3035b02

Changed files:
  drivers/gpu/drm/xe/xe_guc_capture.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=b485bfb45555163bfa5f565d6a3415fcb3035b02

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

The original Linux kernel CVE announcement for CVE-2026-68274 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68274

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: 7

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: YES
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).