[CVE-2026-74451][MODERATE 7.0] drm/panthor: validate firmware interface structure sizes

[CVE-2026-74451][MODERATE 7.0] drm/panthor: validate firmware interface structure sizes

[AL-KERNEL]

CVE: CVE-2026-74451
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: drm/panthor: validate firmware interface structure sizes
Commit: 21c77486f5a60bb9c0433c21de62a5f25d5091f1
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=21c77486f5a60bb9c0433c21de62a5f25d5091f1
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74451
Analysis date: Sat, 15 Aug 2026 10:12:23 -0400
ActionableScore: 6
ActionableScore lower bound: 3
Actionable bucket: Actionable Moderate at minimum. Borderline Strong Important candidate if non-root local users can influence the Panthor firmware interface state
Manual review required: YES

Summary:
A firmware-provided Panthor MCU address was validated only by start address, allowing full interface structures to cross the shared-section boundary and potentially causing kernel out-of-bounds access, with realistic impact of DoS and worst-case concern for memory corruption.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-74451 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74451

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
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CVE-2026-74451	MODERATE	CHECK WITH IMPACT FROM ORIG NN LOW	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-125;*CWE-787;CWE-119;*CWE-20;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'The panthor firmware interface code validated only that a firmware provided MCU virtual address started inside the shared section. If the address points near the end of that section, the returned CPU pointer can still be used as a full interface structure and later field accesses may go out-of-bounds. This is a local GPU driver issue and is not network reachable. For the CVSS the PR:L is used for the paranoid score because some deployments may expose GPU render nodes or firmware mediated GPU control to non root local users, even though reliable control of the firmware interface is not proven. Impact is at least denial of service via invalid kernel memory access and in worst case may allow confidentiality or integrity impact because the bug class is out-of-bounds access in kernel memory.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum. Borderline Strong Important candidate if non-root local users can influence the Panthor firmware interface state (with actual score 5)  SKIP CVE-2026-74451 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	OOB HARDWARE  DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=6
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 6
* Final recommended bucket: **Actionable Moderate at minimum. Borderline Strong Important candidate if non-root local users can influence the Panthor firmware interface state**

## 2. Signal breakdown

Conservative signals:

* Firmware-mediated external influence: +1
  The address comes from firmware-provided MCU virtual addresses, not from ordinary packet or syscall input.
* Memory corruption, Weak/indirect corruption candidate: +1
  The bug allows an object pointer whose start is inside the shared section but whose full structure crosses the boundary, causing out-of-bounds structure accesses.
* Privileged kernel/device-management memory corruption path: +1
  The issue is in a GPU kernel driver firmware interface initialization path.
* Rare AND difficult-to-reach subsystem/configuration: -1
  It requires Panthor hardware and a firmware/shared-memory setup where malformed interface addresses are present.
* Availability impact realistic: +1
  Invalid kernel memory access from malformed firmware interface structures can plausibly crash or break the driver.

Conservative total: 3

Paranoid additional signals:

* Local unprivileged trigger: +1
  Some GPU deployments expose render nodes or GPU job submission paths to non-root local users, but direct control over this firmware interface is not proven.
* Weak LPE concern: +1
  The bug class is kernel out-of-bounds access through a bogus firmware interface structure pointer, which is worth manual review for possible corruption sinks.
* Confidentiality impact plausible: +1
  Out-of-bounds reads from adjacent kernel-mapped memory are plausible in the worst case, although not demonstrated.
* Integrity impact plausible: +1
  Out-of-bounds writes are plausible if the CPU writes to the affected input/control structures beyond the shared section, although target and payload control are unclear.

Paranoid total: 6

## 3. Reachability analysis

This is not remotely network reachable. The immediate source of the bad pointer is firmware-provided MCU virtual addresses inside the Panthor GPU firmware shared section. A conservative interpretation treats triggering as requiring compromised or malformed firmware, device state manipulation, or privileged GPU/device-management influence.

Namespaces and containers do not obviously make the firmware interface directly reachable. However, GPU render nodes are commonly exposed to non-root local users on desktop, mobile, and some containerized GPU workloads. If a local user can indirectly influence firmware interface setup through GPU job submission or device reset paths, PR:L is a defensible paranoid interpretation, but the supplied patch does not prove that path.

The path is hardware and driver specific, not a broad default kernel subsystem. Realistic exploitation depends on Panthor hardware, the affected driver, and whether attacker-controlled or attacker-influenced firmware interface values can be introduced.

Call-site confidence: high. The patch shows the helper and its direct callers for global, CSG, and CS firmware interface structures.

## 4. Severity interpretation

This is stronger than an ordinary validation cleanup because the old helper returned a CPU pointer that was later used as a complete structure without checking that the whole object fit in the shared section. That creates a concrete out-of-bounds access condition in kernel driver code.

Realistically, the main demonstrated risk is driver failure or kernel crash from invalid firmware interface pointers. Theoretical memory corruption risk exists because the returned pointer may be used for structured reads or writes beyond the intended shared memory object. The patch does not demonstrate an arbitrary write, controlled reclaim, type confusion, or reliable LPE primitive, so the conservative score should remain Moderate. The paranoid score should remain Actionable Moderate and require manual review due to kernel OOB access in a GPU firmware interface.

## 5. One-sentence report phrase

A firmware-provided Panthor MCU address was validated only by start address, allowing full interface structures to cross the shared-section boundary and potentially causing kernel out-of-bounds access, with realistic impact of DoS and worst-case concern for memory corruption.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: the patch fixes a concrete bounds-checking bug that can produce out-of-bounds accesses in kernel GPU driver firmware interface structures. The exploitability is not proven, but the combination of firmware-fed pointers, kernel OOB access, and possible local GPU exposure should not be auto-closed.

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

Patch: drm/panthor: validate firmware interface structure sizes
Commit: 21c77486f5a60bb9c0433c21de62a5f25d5091f1
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=21c77486f5a60bb9c0433c21de62a5f25d5091f1

Commit description:

iface_fw_to_cpu_addr() only checks that the firmware-provided MCU virtual
address points inside the shared section. The returned pointer is later
used as a full firmware interface structure, so accepting an address near
the end of the shared section can still lead to out-of-bounds accesses.

Pass the expected object size to iface_fw_to_cpu_addr() and reject ranges
that do not fit entirely in the shared section.

Fixes: 2718d91 ("drm/panthor: Add the FW logical block")
Cc: stable@vger.kernel.org
Signed-off-by: Osama Abdelkader <osama.abdelkader@gmail.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Signed-off-by: Steven Price <steven.price@arm.com>
Link: https://patch.msgid.link/20260720114918.15973-1-osama.abdelkader@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/gpu/drm/panthor/panthor_fw.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=21c77486f5a60bb9c0433c21de62a5f25d5091f1

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

The original Linux kernel CVE announcement for CVE-2026-74451 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74451

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: 3
  Paranoid ActionableScore: 6

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 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).