[CVE-2026-99208][MODERATE 7.0] drm/xe/oa: Zero OA buffer at allocation [ Upstream

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

CVE: CVE-2026-99208
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: drm/xe/oa: Zero OA buffer at allocation [ Upstream
Commit: 21f41b6daf0dbe2cdaaf9f54af6e23fd3c9190b9
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=21f41b6daf0dbe2cdaaf9f54af6e23fd3c9190b9
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99208
Analysis date: Wed, 28 Oct 2026 23:00:22 -0400
ActionableScore: 3
ActionableScore lower bound: unknown
Actionable bucket: Borderline / manual review recommended
Manual review required: YES

Summary:
A permitted local Xe OA client can mmap an uninitialized OA buffer and read stale contents from previously freed pages.

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

The original Linux kernel CVE announcement for CVE-2026-99208 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99208

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.

======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-99208	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-99208 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=2 LEGACY=MODERATE_KPANIC RESULT=SAME V39_AEGIS_ONE_STEP_UP=MODERATE->MODERATE_KPANIC (final reconciliation agrees; DECISION: both MODERATE_KPANIC)	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:N/A:N';CWE-908;*CWE-200;CWE-226;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N';BEST CVSS score: '5.5';DESCR 'An uninitialized Xe OA buffer can expose stale contents from previously freed pages because ttm_bo_type_kernel allocations are not guaranteed to be zeroed. Streams opened with DRM_XE_OA_PROPERTY_OA_DISABLED allocate this mmap capable buffer without passing through xe_oa_init_oa_buffer, allowing an authorized local process to read residual kernel or device memory. For the CVSS the PR:L value is selected because exploitation requires a local process with access to the Xe OA interface and permission to map the buffer. The demonstrated primitive is an information disclosure with no supported integrity or availability impact. Base confidentiality is Low because the stale contents are not shown to be attacker selected, while the paranoid score uses High because repeated allocation and mapping may expose a significant amount of sensitive memory. Automated impact decision path. The original SimpleNet classifier selected MODERATE. The primary LLM estimated paranoid CVSS 5.5 and the production ActionableScore returned 3 with recommendation Borderline / manual review recommended. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were final reconciliation stage MODERATE to MODERATE_KPANIC because the cross model evidence reconciliation rule was applied. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were V39_AEGIS_ONE_STEP_UP and MANUAL_REVIEW_REQUIRED. The independent weaker Aegis shadow evaluated CVSS 3.3 and ActionableScore 2 with primitive class NONE and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. Cross model aggregation changed the production result under an enabled evidence gated merge rule. The final reported impact is MODERATE_KPANIC.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 3)	MAYBE	READ LEAK UAF HARDWARE  KPANIC V39_AEGIS_ONE_STEP_UP MANUAL_REVIEW_REQUIRED	-	-	checked

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

ActionableScore=3
PrimitiveClass=CLASS_B
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
RequiresHostUID0=NO
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=CONFIRMED
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw base score: 3.
* Conservative score: 3; no floor or cap applied.
* Raw paranoid score: 3.
* Paranoid score: 3; possible larger disclosure through repeated allocations is not separately scored without evidence about recovered contents.
* Final recommended bucket: **Borderline / manual review recommended**::

2. Signal breakdown

* +1 Local below-host-admin trigger: supplied evidence identifies an authorized local process with Xe OA interface and mmap permission; host UID 0 is not required.
* +1 Confidentiality plausible: the commit explicitly confirms that non-zeroed BO pages become readable through the userspace-mappable OA buffer.
* +1 Practical disclosure chain: `OA_DISABLED` skips initialization, allocation retains stale page contents, and mmap exposes those bytes.
* No negative penalty: Intel Xe hardware is required, but it is not shown to be rare or physical-attacker-only.
* No Class A/major-disclosure bonus: attacker-selected contents, credentials, keys, cross-process secrets, or a reliably large disclosure are not shown.
* No integrity, availability, UAF, OOB write, authorization bypass, or privilege-escalation signal is supported.

3. Reachability analysis

The supported actor is a local, below-host-admin process authorized to open the Xe OA interface and map its OA buffer. The exact device-node permission model and any namespace relationship are not supplied, so namespace-scoped privilege remains unknown. The trigger requires an Intel Xe device and an OA stream created with `DRM_XE_OA_PROPERTY_OA_DISABLED`; no race, special timing, or separate privileged setup is shown.

4. Primitive and severity reading

The primitive is a direct userspace disclosure from uninitialized, mmap-visible kernel/device BO pages. It is CLASS_B because disclosure is real, but the sensitivity and amount of recovered stale data are uncontrolled and unresolved. This is not an authorization DENY-to-ALLOW flaw, so B4-PENDING does not apply. ImportantCandidate is NO and auto-downgrade is allowed because no major disclosure target or stronger boundary effect is established.

5. One-sentence report phrase

A permitted local Xe OA client can mmap an uninitialized OA buffer and read stale contents from previously freed pages.

6. Manual review advice

MANUAL CHECK RECOMMENDED

Confirm production Xe OA device permissions and whether repeated allocation permits reliable recovery of sensitive kernel or peer-process data.

7. Call-site confidence

Call-site confidence: medium

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

Patch: drm/xe/oa: Zero OA buffer at allocation [ Upstream
Commit: 21f41b6daf0dbe2cdaaf9f54af6e23fd3c9190b9
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=21f41b6daf0dbe2cdaaf9f54af6e23fd3c9190b9

Changed files:
  drivers/gpu/drm/xe/xe_oa.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=21f41b6daf0dbe2cdaaf9f54af6e23fd3c9190b9

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

The original Linux kernel CVE announcement for CVE-2026-99208 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99208

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:L/UI:N/S:U/C:L/I:N/A:N
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
  The Best / paranoid CVSS score: 5.5

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: unknown
  Paranoid ActionableScore: 3

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).