[CVE-2026-80908][MODERATE 7.0] drm/amdgpu: Reject UVD message with dimensions above 4096

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

CVE: CVE-2026-80908
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: drm/amdgpu: Reject UVD message with dimensions above 4096
Commit: 8bae80eaed00e7ae28412a3cdf590f4beca72294
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8bae80eaed00e7ae28412a3cdf590f4beca72294
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80908
Analysis date: Fri, 04 Sep 2026 18:23:33 -0400
ActionableScore: 5
ActionableScore lower bound: 3
Actionable bucket: Actionable Moderate
Manual review required: NO

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-80908 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80908

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: NO

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

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

CVE-2026-80908	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-80908 CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H';CWE-190;*CWE-20;CWE-680;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '6.6';DESCR 'An integer overflow risk in the AMDGPU UVD command validation path can occur because UVD messages accepted decoding dimensions above 4096 and those dimensions are later used in DPB size calculations. A local user with access to the DRM render device can submit a crafted UVD decode message and potentially make the driver calculate an incorrect DPB size. The most direct impact is denial of service through GPU fault, driver reset, or kernel instability. Because the affected values are used for buffer size validation in a hardware command path, limited confidentiality or integrity impact is defensible for paranoid scoring, but full privilege escalation is not proven from this small diff alone. For the CVSS the PR:L because reliable triggering requires local code execution with access to the DRM render node or video acceleration interface. The issue is not network reachable.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate (with actual score 4)  SKIP CVE-2026-80908 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	SIMPLEFIX HARDWARE  INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP	-	-	checked

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

ActionableScore=5
ActionableScoreLower=3
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=NO

1. ActionableScore

* Raw conservative score: 3
* Conservative score: 3
* Raw paranoid score: 5
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate**::

No floor was applied. The validation-only cap is respected: conservative remains below 4 and paranoid remains at 5.

2. Signal breakdown

Conservative signals:

* +1 Local below-host-admin reachability: AMDGPU UVD command submission is plausibly reachable by a local user or graphics/video process with access to the DRM render device, not necessarily host administrator.
* +1 Weak / indirect corruption candidate: the patch explicitly says the upper bound prevents a potential overflow in DPB size calculations.
* +1 Broad practical subsystem path: AMDGPU video decode is not rare physical-only hardware and can be exercised on common systems with supported AMD GPUs.

Conservative non-awarded signals:

* Strong corruption +2 not awarded: no concrete OOB write, arbitrary write, controlled overwrite, controlled reclaim, or callback influence is shown.
* Reliable kernel crash +1 not awarded conservatively: the supplied patch says potential overflow, but does not show a concrete panic trace or guaranteed host-wide crash.
* Confidentiality and integrity not awarded conservatively: no disclosure path, unauthorized write, or protected object corruption is directly established.
* Remote reachability not awarded: this is a local DRM/GPU command submission path, not network packet processing.
* Hardware rarity penalty not applied: AMD GPU support is hardware-specific, but not rare or physical-attacker-only.

Paranoid additional signals:

* +1 Local high-control kernel data-plane API: the attacker-controlled UVD message supplies width and height values that directly affect DPB size calculation, which is exploitation-relevant input control.
* +1 Memory layout invariant restoration: the fix restores a size-calculation invariant by bounding dimensions before DPB sizing, so the risk is more than a harmless ordinary value mismatch.

Paranoid non-awarded signals:

* Strong LPE leverage +2 not awarded: no controlled memory corruption or privilege-escalation primitive is established.
* C/I impact not separately awarded: limited C/I may be defensible in CVSS-style paranoid scoring, but ActionableScore requires a more concrete disclosure or integrity primitive.
* Extra availability not awarded: no distinct persistent availability mechanism beyond possible GPU fault or kernel instability is established.
* UAF-related signals not awarded: this patch does not establish UAF, stale pointer use, double release, or repeated refcount mutation.

3. Reachability analysis

The evaluated attacker is a local user or local graphics/video process that can submit UVD decode command messages through the AMDGPU DRM interface. This is below host-admin in typical render-node deployments, so HostAdminRequired=NO.

The issue is not namespace-scoped. DRM render device access is governed by device node permissions and graphics stack policy, not by an attacker-created user or network namespace. NamespaceScopedPrivilege=NO.

No prior privileged setup is required beyond the system having AMDGPU and UVD support enabled and the attacker having access to the relevant DRM device node. This is not a network-reachable issue. No hard race is involved. The trigger is input validation of dimensions in a submitted UVD message.

For DRM roles: ordinary logged-in users may or may not have render-node access depending on local policy. A compositor or delegated graphics service may have access. Host administrator rights are not inherently required once the device node is exposed to the user or service.

4. Primitive and severity interpretation

The exact primitive is an attacker-controlled integer overflow candidate in DPB size calculations caused by accepting UVD decode dimensions above 4096. This is not a real UAF and not an established arbitrary write.

The primitive is best classified as CLASS_C: invalid arithmetic state / validation failure with possible downstream DoS or constrained memory-safety concern. It is not CLASS_A because no strong exploitation primitive is shown. It is not CLASS_B because the supplied evidence does not directly establish real kernel memory corruption, lifetime violation, stale object use, or a concrete overwrite.

The demonstrated consequence is prevention of a potential overflow. The practical likely impact is GPU fault, driver instability, or kernel-side denial of service if the incorrect DPB size calculation causes invalid command validation. The speculative consequence is limited memory-safety impact in the GPU command-validation path, but full privilege escalation is not proven.

ImportantCandidate=NO because no strong corruption, controlled overwrite, UAF, COW violation, authorization bypass, or demonstrated LPE is established. AutoDowngradeAllowed=NO because this is still an actionable validation bug in a GPU command path with attacker-controlled size-calculation input, so automatic closure as harmless would risk missing a real memory-safety issue.

Likely operational severity: actionable Moderate.

5. One-sentence report phrase

An AMDGPU UVD validation flaw allowed decode messages with dimensions above 4096, creating a potential integer overflow in DPB size calculations that a local user with DRM render access could use to cause GPU or kernel instability.

6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Reason: the patch is small and validation-only, but it explicitly fixes a potential integer overflow in a GPU command-validation path with attacker-controlled dimensions.

7. Call-site confidence

Call-site confidence: medium

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

Patch: drm/amdgpu: Reject UVD message with dimensions above 4096
Commit: 8bae80eaed00e7ae28412a3cdf590f4beca72294
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8bae80eaed00e7ae28412a3cdf590f4beca72294

Commit description:

Fixes potential overflow in DPB size calculations.

Signed-off-by: David Rosca <david.rosca@amd.com>
Acked-by: Leo Liu <leo.liu@amd.com>
Reviewed-by: Ruijing Dong <ruijing.dong@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 05e1387 )
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/gpu/drm/amd/amdgpu/amdgpu_uvd.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=8bae80eaed00e7ae28412a3cdf590f4beca72294

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

The original Linux kernel CVE announcement for CVE-2026-80908 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80908

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:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS score: 6.6

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: 3
  Paranoid ActionableScore: 5

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).