---
id: CVE-2026-80578
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  fbdev: core: Fix pointer desynchronization in fb_io_read()

  In fb_io_read(), if copy_to_user() performs a partial copy (e.g., due to
  a faulty user buffer), the loop adj…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  fbdev: core: Fix pointer desynchronization in fb_io_read()

  In fb_io_read(), if copy_to_user() performs a partial copy (e.g., due to
  a faulty user buffer), the loop adj…
severity: high
cvss: 7.3
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H'
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 6121cd9ef911432b14c2a17aefaf8cd2f3cfcdff <
    42bc07b4e5a3c8a02a433388f562a8f46d093e11
  - >-
    Linux >= 6121cd9ef911432b14c2a17aefaf8cd2f3cfcdff <
    42a6d8126c194133eafab2b0fd5c8668ebfcba5b
  - >-
    Linux >= 6121cd9ef911432b14c2a17aefaf8cd2f3cfcdff <
    7ff87a01ae3a8cd0208f7499386998223a8b5dba
  - >-
    Linux >= 6121cd9ef911432b14c2a17aefaf8cd2f3cfcdff <
    7110b7b794a2aac2c5cf8eb06ebf2af724c74d50
  - >-
    Linux >= 6121cd9ef911432b14c2a17aefaf8cd2f3cfcdff <
    81cc73be40c6f028f1ee3f438ace46afe666dbae
  - Linux 6.5
published: '2026-08-26'
updated: '2026-10-16'
sourceUpdated: '2026-10-16T20:18:01.013'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-80578'
references:
  - url: 'https://git.kernel.org/stable/c/42a6d8126c194133eafab2b0fd5c8668ebfcba5b'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/42bc07b4e5a3c8a02a433388f562a8f46d093e11'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/7110b7b794a2aac2c5cf8eb06ebf2af724c74d50'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/7ff87a01ae3a8cd0208f7499386998223a8b5dba'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/81cc73be40c6f028f1ee3f438ace46afe666dbae'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
  - cve.org
epss: 0.00117
epssPercentile: 0.01635
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-10-16T19:17:44.203506Z'
ingestedAt: '2026-10-16T19:46:24.313Z'
---

## Overview

In the Linux kernel, the following vulnerability has been resolved:

fbdev: core: Fix pointer desynchronization in fb_io_read()

In fb_io_read(), if copy_to_user() performs a partial copy (e.g., due to
a faulty user buffer), the loop adjusts the chunk size 'c' and updates
the remaining 'count'. However, the hardware 'src' pointer has already
been eagerly advanced by the original chunk size.

If the loop is allowed to continue, the read will resume from an
incorrect, over-advanced offset. Since the remaining 'count' was only
decremented by the successful bytes, this desynchronization causes the
next iterations to execute more hardware reads than originally bounded,
eventually leading to out-of-bounds I/O reads.

Fix this by breaking out of the loop immediately upon a partial
copy_to_user(). A partial copy indicates a faulty user buffer, making
subsequent read attempts futile. Breaking out ensures we return the
number of successfully read bytes without risking out-of-bounds hardware
accesses in subsequent mismatched iterations.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.