CVE-2026-80551

Guest-to-host compromise via mutable first IDAW

Published Aug 26, 2026 · Updated Aug 27, 2026

A TOCTOU race in the s390 vfio_ccw component of the Linux kernel allows guest OS users to compromise the host through I/O. Between ccw_count_idaws() and get_guest_idal(), the host rereads a guest-controlled first IDAW without confirming that its address is unchanged. A guest needs an assigned VFIO-ccw mediated subchannel; racing another vCPU can expose or corrupt host memory and panic or hang the hypervisor.

CVSS severity9.3
Critical
EPSS probability0.14%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

A TOCTOU race in the s390 vfio_ccw component of the Linux kernel allows guest OS users to compromise the host through I/O. Between ccw_count_idaws() and get_guest_idal(), the host rereads a guest-controlled first IDAW without confirming that its address is unchanged. A guest needs an assigned VFIO-ccw mediated subchannel; racing another vCPU can expose or corrupt host memory and panic or hang the hypervisor.

The record

CVE
CVE-2026-80551
Published
Aug 26, 2026
Updated
Aug 27, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-367, T1068
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 26, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 27, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=01aa26c672c0eb771de4aaa2a8ccf6055778887b <08ef2a82115690d6e229615872ac1731af732497
  2. Affected versionversion=01aa26c672c0eb771de4aaa2a8ccf6055778887b <0d46c2565f173bcddcdcaf44a4f69789a20535e2
  3. Affected versionversion=01aa26c672c0eb771de4aaa2a8ccf6055778887b <460b977a4e71cc319fdadf91c193ec3beaa57263
  4. Affected versionversion=01aa26c672c0eb771de4aaa2a8ccf6055778887b <565bef268d75bf7df665bce6923a88cd0eb74592
  5. Affected versionversion=01aa26c672c0eb771de4aaa2a8ccf6055778887b <fc59e9482117ebdccd6dc7fa8082f8b980fd021e
  6. Affected versionversion=5.3

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=01aa26c672c0eb771de4aaa2a8ccf6055778887b <08ef2a82115690d6e229615872ac1731af732497; version=01aa26c672c0eb771de4aaa2a8ccf6055778887b <0d46c2565f173bcddcdcaf44a4f69789a20535e2; version=01aa26c672c0eb771de4aaa2a8ccf6055778887b <460b977a4e71cc319fdadf91c193ec3beaa57263; version=01aa26c672c0eb771de4aaa2a8ccf6055778887b <565bef268d75bf7df665bce6923a88cd0eb74592; version=01aa26c672c0eb771de4aaa2a8ccf6055778887b <fc59e9482117ebdccd6dc7fa8082f8b980fd021e; version=5.3

Published CVSS scores

9.3LinuxCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
5.5Red HatCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-367Time-of-check Time-of-use (TOCTOU) Race Condition
T1068Exploitation for Privilege Escalation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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