[CVE-2026-98914][MODERATE REGULAR] drm/amdgpu: cap ATOM command table nesting depth [ Upstream

[CVE-2026-98914][MODERATE REGULAR] drm/amdgpu: cap ATOM command table nesting depth [ Upstream

[AL-KERNEL]

CVE: CVE-2026-98914
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: drm/amdgpu: cap ATOM command table nesting depth [ Upstream
Commit: b1d2b29d3115b36efba0976cb5ca3d794c58eead
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b1d2b29d3115b36efba0976cb5ca3d794c58eead
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98914
Analysis date: Tue, 27 Oct 2026 03:34:46 -0400
ActionableScore: 1
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
Excessively nested or recursive AMD ATOM command tables can exhaust the kernel stack, with host denial of service shown but no controlled corruption or privilege escalation established.

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

The original Linux kernel CVE announcement for CVE-2026-98914 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98914

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: NO

A detailed explanation of the methodology and priority rules is included
at the end of this message.

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

CVE-2026-98914	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-98914 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=1 LEGACY=MODERATE RESULT=DIFF (final Legacy and Aegis differ; FINAL: MODERATE, Aegis: MODERATE_KPANIC)	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:H';CWE-674;CWE-121;**CWE-400;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.6';DESCR 'An unbounded ATOM_OP_CALLTABLE chain can recursively enter amdgpu_atom_execute_table_locked until the kernel stack is exhausted, causing at least a kernel panic or host denial of service. The command graph normally comes from the GPU VBIOS. A local DRM client may cause existing firmware paths to execute but cannot normally define the recursive table graph. For the CVSS the PR:H value reflects that reliable software based triggering generally requires administrative control to replace or override the VBIOS, while a malicious physical device is a separate deployment threat. The base score uses availability impact only. The paranoid score allows limited confidentiality and integrity impact because kernel stack overflow can corrupt stack data on configurations lacking effective guard containment, although no controlled write or demonstrated privilege escalation primitive is established. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. The primary LLM estimated paranoid CVSS 5.6 and the production ActionableScore returned 1 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were ActionableScore thresholds stage MODERATE_KPANIC to MODERATE because the ActionableScore threshold 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 DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 and V41_INHERITED_KPANIC_PROMOTION_BLOCKED and MANUAL_REVIEW_REQUIRED. The independent weaker Aegis shadow evaluated CVSS 2.0 and ActionableScore 1 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. The models disagreed but the aggregation rules retained the production result. The final reported impact is MODERATE.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1)	MAYBE	OOB HARDWARE  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 V41_INHERITED_KPANIC_PROMOTION_BLOCKED MANUAL_REVIEW_REQUIRED	-	-	checked

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

ActionableScore=1
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw base score: 1.
* Conservative score: 1; no floor or cap applied.
* Raw paranoid score: 1.
* Paranoid score: 1; speculative stack corruption was not scored.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

* +1 Reliable kernel crash / strong DoS: recursive `ATOM_OP_CALLTABLE` execution can exhaust the kernel stack; the new depth limit directly prevents this.
* No privilege penalty: administrative VBIOS replacement is described as the reliable software trigger, but the complete trigger model also includes existing firmware paths and possible physical-device influence, so host-admin necessity is not conclusively established.
* No OOB-write score: the patch proves unbounded recursion and stack exhaustion, not a confirmed attacker-influenced heap/slab or directed stack write.
* No confidentiality or integrity score: guard-page bypass, controlled stack corruption, disclosure, and privilege escalation are not demonstrated.
* No B5-R: there is no retry-accumulated heap OOB write or later consumption of corrupted structured state.
* No authorization signal: the added condition is a recursion safety bound, not a DENY-to-ALLOW security guard.

3. Reachability analysis

A local DRM client may invoke existing ATOM firmware command paths, but supplied evidence says it cannot normally define the recursive command graph. Reliable software construction apparently requires privileged VBIOS replacement or override, while a malicious physical device is a separate possibility. The complete attacker privilege, UID requirement, and any namespace-scoped path therefore remain unknown. No race is required; recursion is deterministic once a cyclic or excessively nested table is executed.

4. Primitive and severity reading

The exact shown primitive is uncontrolled recursive kernel execution leading to stack exhaustion and plausible host crash. It is Class C crash/DoS behavior, not a real UAF, confirmed OOB write, or active corrupted-state consumer. Stronger stack-data corruption is theoretical only. ImportantCandidate is NO because no separately useful corruption or boundary primitive is established. Auto-downgrade is allowed, although trigger provenance should be checked manually.

5. One-sentence report phrase

Excessively nested or recursive AMD ATOM command tables can exhaust the kernel stack, with host denial of service shown but no controlled corruption or privilege escalation established.

6. Manual review advice

MANUAL CHECK RECOMMENDED

Confirm whether any supported unprivileged DRM operation can reliably reach a recursive table in deployed firmware without privileged firmware replacement.

7. Call-site confidence

Call-site confidence: medium

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

Patch: drm/amdgpu: cap ATOM command table nesting depth [ Upstream
Commit: b1d2b29d3115b36efba0976cb5ca3d794c58eead
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b1d2b29d3115b36efba0976cb5ca3d794c58eead

Changed files:
  drivers/gpu/drm/amd/amdgpu/atom.c
  drivers/gpu/drm/amd/amdgpu/atom.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=b1d2b29d3115b36efba0976cb5ca3d794c58eead

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

The original Linux kernel CVE announcement for CVE-2026-98914 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98914

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:H/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS score: 5.6

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: 1

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).