[CVE-2026-80786][LOW] fbdev: Wrap user-invoked calls to fb_set_var() in helper [ Upstream

[CVE-2026-80786][LOW] fbdev: Wrap user-invoked calls to fb_set_var() in helper [ Upstream

[AL-KERNEL]

CVE: CVE-2026-80786
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: fbdev: Wrap user-invoked calls to fb_set_var() in helper [ Upstream
Commit: 07f7e46833f71472e30da54a50dacdf48521bdd3
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=07f7e46833f71472e30da54a50dacdf48521bdd3
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80786
Analysis date: Fri, 04 Sep 2026 18:17:47 -0400
ActionableScore: 2
ActionableScore lower bound: 0
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: YES

Summary:
Some fbdev mode-change paths did not consistently validate requested modes with fbcon and update virtual consoles after applying framebuffer state, which could cause local display or console availability problems for users able to access framebuffer configuration interfaces.

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

The original Linux kernel CVE announcement for CVE-2026-80786 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80786

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: LOW
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-2026-80786	LOW	https://www.kernelcve.org/list/?q=CVE-2026-80786 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:N/I:N/A:L';CWE-703;CWE-754;*CWE-20;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '3.3';DESCR 'fbdev mode changes from some user reachable paths did not consistently ask fbcon whether the requested mode was acceptable before applying the framebuffer state and updating virtual consoles. This can leave fbcon and the framebuffer device in an inconsistent state and may cause local console malfunction or display availability problems. For the CVSS the PR:L reflects environments where a local user can access fbdev ioctls or mode setting interfaces through a video group or delegated device permissions. The issue is not network reachable and is triggered through local framebuffer configuration paths rather than packet traffic. Impact is limited denial of service for local display or console state, with no concrete evidence of information disclosure, memory corruption, or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1)	YES	HARDWARE 	NO	NO	checked

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

ActionableScore=2
ActionableScoreLower=0

## 1. ActionableScore

* Conservative score: 0
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate / Low-like**

## 2. Signal breakdown

Conservative signals:

* Requires admin/root/CAP_* in typical deployments: -2. Sysfs mode setting and many framebuffer configuration paths are normally restricted or device-permission gated.
* Availability impact realistic: +1. The plausible impact is local display or virtual-console malfunction, not a reliable system-wide kernel crash.
* Broad/default/common subsystem: +1 could be considered weakly applicable because fbdev/fbcon is common on some systems, but modern exposure is often limited and hardware dependent.

Paranoid signals:

* Local unprivileged or low-privileged trigger: +1. Some deployments expose /dev/fb* to local users through the video group or similar delegated device permissions.
* Availability impact realistic: +1. A user-triggered mode change may leave fbcon and framebuffer state inconsistent, causing local console/display availability issues.

Not awarded:

* No remote/network trigger.
* No UAF, OOB write, double free, refcount bug, stale callback, or type confusion.
* No confidentiality or integrity impact.
* No privilege escalation plausibility.
* No strong DoS signal because the patch does not show a kernel panic, Oops, lockup, or persistent host-wide failure.

Call-site confidence: high. The patch shows the relevant callers in fb_chrdev, fbsysfs, ps3fb, and sh_mobile_lcdcfb.

## 3. Reachability analysis

The bug is reachable through local framebuffer mode-change paths. FBIOPUT_VSCREENINFO already performed fbcon validation and update steps, while other sysfs and driver paths could call fb_set_var without the full fbcon coordination. In typical deployments, changing these settings requires administrative access or membership in a device-access group such as video. Containers usually do not expose real framebuffer devices unless explicitly delegated, so namespace-based reachability is limited. The path is not network reachable.

## 4. Severity interpretation

This behaves like a low-end Moderate or Low-like local availability issue. The patch fixes inconsistent fbcon handling around mode changes, not memory lifetime, bounds checking, or attacker-controlled kernel memory corruption. Theoretical impact is limited to incorrect console/display state or local display DoS. Realistic exploitation evidence for privilege escalation, information disclosure, kernel memory corruption, or host-wide crash is not present.

## 5. One-sentence report phrase

Some fbdev mode-change paths did not consistently validate requested modes with fbcon and update virtual consoles after applying framebuffer state, which could cause local display or console availability problems for users able to access framebuffer configuration interfaces.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED.
NO MANUAL CHECK REQUIRED COULD BE AUTOCLOSED because the patch shows a local consistency fix with limited availability impact and no supported memory corruption or privilege escalation primitive.

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

Patch: fbdev: Wrap user-invoked calls to fb_set_var() in helper [ Upstream
Commit: 07f7e46833f71472e30da54a50dacdf48521bdd3
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=07f7e46833f71472e30da54a50dacdf48521bdd3

Changed files:
  drivers/video/fbdev/core/fb_chrdev.c
  drivers/video/fbdev/core/fbcon.c
  drivers/video/fbdev/core/fbmem.c
  drivers/video/fbdev/core/fbsysfs.c
  drivers/video/fbdev/ps3fb.c
  drivers/video/fbdev/sh_mobile_lcdcfb.c
  include/linux/fb.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=07f7e46833f71472e30da54a50dacdf48521bdd3

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

The original Linux kernel CVE announcement for CVE-2026-80786 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80786

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:L
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS score: 3.3

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: 0
  Paranoid ActionableScore: 2

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: LOW
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): LOW

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).