CVE-2026-80550: s390/vfio_ccw: Fix out of bounds check on CCW array

mediumCVSS 5.5CVE-2026-80550

CSIRTS triage

vendor: Linux product: Linux Kernel Memory corruption

What: An out-of-bounds check on a CCW (Channel Command Word) array in s390/vfio_ccw is missing or incorrect.
Who is affected: Systems running Linux kernel with s390 architecture and vfio_ccw support enabled.
Urgency: Medium priority; CVSS 5.5 indicates moderate impact and should be patched in standard update cycles.
Action: Apply a Linux kernel update that fixes the bounds checking logic for CCW arrays.

AI-assisted analysis generated from the source advisory — verify against the original.

⚡ Watch Linux Kernel

Get an email when a new Linux Kernel advisory drops — max one per day, one-click unsubscribe.

Details

Source: Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity: medium — CVSS 5.5
Published: 2026-08-11
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-80550

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-805500.14% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 3% of all EPSS-scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-80550	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

Recent advisories for s390/vfio_ccw

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

highCVE-2026-80555: In the Linux kernel, the following vulnerability has been resolved: s390/vfio_ccw: Free all me…nvd · 2026-08-26
criticalCVE-2026-80554: In the Linux kernel, the following vulnerability has been resolved: s390/vfio_ccw: Limit the n…nvd · 2026-08-26
highCVE-2026-80553: In the Linux kernel, the following vulnerability has been resolved: s390/vfio_ccw: Cancel exis…nvd · 2026-08-26
highCVE-2026-80552: In the Linux kernel, the following vulnerability has been resolved: s390/vfio_ccw: Ensure inde…nvd · 2026-08-26
criticalCVE-2026-80551: In the Linux kernel, the following vulnerability has been resolved: s390/vfio_ccw: Ensure firs…nvd · 2026-08-26
highCVE-2026-80550: In the Linux kernel, the following vulnerability has been resolved: s390/vfio_ccw: Fix out of …nvd · 2026-08-26