---
id: CVE-2026-80550
title: 's390/vfio_ccw: Fix out of bounds check on CCW array'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  s390/vfio_ccw: Fix out of bounds check on CCW array

  The routine ccwchain_calc_length() counts the number of channel
  command words (CCWs) that are chained together in a…
severity: high
cvss: 7.9
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:L'
cvssSource: cna
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 0a19e61e6d4c6192077ead760ba0a2d350987d4c <
    0282fb1c4b638eecfe2cc558092c460911d8f7e2
  - >-
    Linux >= 0a19e61e6d4c6192077ead760ba0a2d350987d4c <
    907adc667d902fafbdb2d740d57b55bd025dc4cd
  - >-
    Linux >= 0a19e61e6d4c6192077ead760ba0a2d350987d4c <
    f20be33d093ce7630c17ff7ed93caf7eaf8ac1a3
  - >-
    Linux >= 0a19e61e6d4c6192077ead760ba0a2d350987d4c <
    af3f80ca4c8b17f20f9e588def076288fdb49e65
  - >-
    Linux >= 0a19e61e6d4c6192077ead760ba0a2d350987d4c <
    499a8a66b1598bfab97182aed15e0f1646074a3d
  - >-
    Linux >= 0a19e61e6d4c6192077ead760ba0a2d350987d4c <
    4c2e1d359d7a2b82cdf3254e4e480af9417f99fb
  - >-
    Linux >= 0a19e61e6d4c6192077ead760ba0a2d350987d4c <
    d5d096cd9369e986d4e5153baa86b8b35c283e09
  - >-
    Linux >= 0a19e61e6d4c6192077ead760ba0a2d350987d4c <
    a005b7f1a491ffda61bff0fd0f6548f8986fb977
  - Linux 4.12
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-10-16T19:17:08.790140Z'
published: '2026-08-26'
updated: '2026-10-16'
sourceUpdated: '2026-10-16T19:26:26.153Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-80550'
references:
  - url: 'https://git.kernel.org/stable/c/0282fb1c4b638eecfe2cc558092c460911d8f7e2'
  - url: 'https://git.kernel.org/stable/c/907adc667d902fafbdb2d740d57b55bd025dc4cd'
  - url: 'https://git.kernel.org/stable/c/f20be33d093ce7630c17ff7ed93caf7eaf8ac1a3'
  - url: 'https://git.kernel.org/stable/c/af3f80ca4c8b17f20f9e588def076288fdb49e65'
  - url: 'https://git.kernel.org/stable/c/499a8a66b1598bfab97182aed15e0f1646074a3d'
  - url: 'https://git.kernel.org/stable/c/4c2e1d359d7a2b82cdf3254e4e480af9417f99fb'
  - url: 'https://git.kernel.org/stable/c/d5d096cd9369e986d4e5153baa86b8b35c283e09'
  - url: 'https://git.kernel.org/stable/c/a005b7f1a491ffda61bff0fd0f6548f8986fb977'
tags:
  - cve.org
epss: 0.00181
epssPercentile: 0.07216
ingestedAt: '2026-10-16T19:46:24.316Z'
---

## Overview

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

s390/vfio_ccw: Fix out of bounds check on CCW array

The routine ccwchain_calc_length() counts the number of channel
command words (CCWs) that are chained together in a single channel
program, and rejects anything larger than CCWCHAIN_LEN_MAX (256) CCWs.

The loop itself is "do..while (count < 257)", and while the logic in
is_cpa_within_range() correctly adjusts between the 0-index array of
CCWs and the count of CCWs starting at 1, this means it would look
at a possible 257th CCW before ending the loop and (correctly)
returning an error.

Fix this by restructuring the loop to break as soon as 256 CCWs
(thus indexes 0-255) are examined, without looking at memory
outside the range.

## Affected

- `Linux >= 0a19e61e6d4c6192077ead760ba0a2d350987d4c < 0282fb1c4b638eecfe2cc558092c460911d8f7e2`
- `Linux >= 0a19e61e6d4c6192077ead760ba0a2d350987d4c < 907adc667d902fafbdb2d740d57b55bd025dc4cd`
- `Linux >= 0a19e61e6d4c6192077ead760ba0a2d350987d4c < f20be33d093ce7630c17ff7ed93caf7eaf8ac1a3`
- `Linux >= 0a19e61e6d4c6192077ead760ba0a2d350987d4c < af3f80ca4c8b17f20f9e588def076288fdb49e65`
- `Linux >= 0a19e61e6d4c6192077ead760ba0a2d350987d4c < 499a8a66b1598bfab97182aed15e0f1646074a3d`
- `Linux >= 0a19e61e6d4c6192077ead760ba0a2d350987d4c < 4c2e1d359d7a2b82cdf3254e4e480af9417f99fb`
- `Linux >= 0a19e61e6d4c6192077ead760ba0a2d350987d4c < d5d096cd9369e986d4e5153baa86b8b35c283e09`
- `Linux >= 0a19e61e6d4c6192077ead760ba0a2d350987d4c < a005b7f1a491ffda61bff0fd0f6548f8986fb977`
- `Linux 4.12`

## Remediation

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