CVE-2025-40026

Host panic via repeated L1 intercept evaluation

Published Oct 28, 2025 · Updated Oct 28, 2025

Denial of service in affected Linux KVM x86 kernels allows local users or guest OS users to panic the host via nested port I/O. The userspace-I/O completion path rechecks L1 intercepts after committing L2 I/O, so a changed permission bitmap leaves vcpu->arch.pio.count uncleared. Access to /dev/kvm or code execution in a guest running a nested hypervisor is required; stale I/O data can also cross the L1/L2 boundary.

CVSS severity7.9
High
EPSS probability0.16%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in affected Linux KVM x86 kernels allows local users or guest OS users to panic the host via nested port I/O. The userspace-I/O completion path rechecks L1 intercepts after committing L2 I/O, so a changed permission bitmap leaves vcpu->arch.pio.count uncleared. Access to /dev/kvm or code execution in a guest running a nested hypervisor is required; stale I/O data can also cross the L1/L2 boundary.

The record

CVE
CVE-2025-40026
Published
Oct 28, 2025
Updated
Oct 28, 2025
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Oct 28, 2025CVE publishedPublication date reported by the CVE source.
  2. Oct 28, 2025Record 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=3.0
  2. Affected versionversion=8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9 <3a062a5c55adc5507600b9ae6d911e247e2f1d6e
  3. Affected versionversion=8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9 <3d3abf3f7e8b1abb082070a343de82d7efc80523
  4. Affected versionversion=8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9 <7366830642505683bbe905a2ba5d18d6e4b512b8
  5. Affected versionversion=8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9 <ba35a5d775799ce5ad60230be97336f2fefd518e
  6. Affected versionversion=8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9 <e0ce3ed1048a47986d15aef1a98ebda25560d257
  7. Affected versionversion=8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9 <e7177c7e32cb806f348387b7f4faafd4a5b32054
  8. Affected versionversion=8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9 <e750f85391286a4c8100275516973324b621a269

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=3.0; version=8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9 <3a062a5c55adc5507600b9ae6d911e247e2f1d6e; version=8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9 <3d3abf3f7e8b1abb082070a343de82d7efc80523; version=8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9 <7366830642505683bbe905a2ba5d18d6e4b512b8; version=8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9 <ba35a5d775799ce5ad60230be97336f2fefd518e; version=8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9 <e0ce3ed1048a47986d15aef1a98ebda25560d257; version=8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9 <e7177c7e32cb806f348387b7f4faafd4a5b32054; version=8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9 <e750f85391286a4c8100275516973324b621a269

Published CVSS scores

7.9Linux Kernel CVE TeamCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/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.

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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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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