CVE-2026-80550
Received Received - Intake

Out-of-Bounds Access in Linux Kernel s390/vfio_ccw

Publication date: 2026-08-26

Last updated on: 2026-08-26

Assigner: kernel.org

Description
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.

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Meta Information

Published
2026-08-26
Last Modified
2026-08-26
Generated
2026-08-26
AI Q&A
2026-08-26
EPSS Evaluated
N/A
NVD
CVE-2026-80550
EUVD
EUVD-2026-66465

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel *

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This is a vulnerability in the Linux kernel's s390/vfio_ccw component. It involves an out-of-bounds check error in the ccwchain_calc_length() routine, which counts chained channel command words (CCWs). The loop incorrectly examines up to a 257th CCW before terminating, potentially accessing memory outside the valid range of 256 CCWs (indexes 0-255).

Detection Guidance

This vulnerability is specific to the Linux kernel's s390/vfio_ccw driver and involves an out-of-bounds check on the CCW array. Detection requires checking the kernel version and verifying if the vulnerable code path is present. No direct network or system commands are provided in the context to detect this issue.

Impact Analysis

This vulnerability could allow an attacker to cause a denial-of-service condition or potentially execute arbitrary code by triggering an out-of-bounds memory access. It affects systems using the s390/vfio_ccw driver, which is specific to IBM Z (s390x) architectures.

Mitigation Strategies

Apply the kernel patch that fixes the out-of-bounds check in the s390/vfio_ccw driver. Update to a version of the Linux kernel that includes the fix for CVE-2026-80550. Monitor vendor advisories for kernel updates.

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