CVE-2026-63806

Host crash via unaligned ioeventfd datamatch

Published Jul 19, 2026 · Updated Jul 19, 2026

Reachable assertion in affected Linux Kernel releases allows guest OS users to crash the host via a crafted MMIO store. KVM's ioeventfd_write path directly dereferences a misaligned datamatch value after an emulated store crosses a page boundary, causing BUG_ON to fire. Unprivileged code in a KVM guest with a datamatch-enabled ioeventfd is sufficient, and the resulting host failure interrupts co-resident virtual machines.

CVSS severity7.1
High
EPSS probability0.15%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Reachable assertion in affected Linux Kernel releases allows guest OS users to crash the host via a crafted MMIO store. KVM's ioeventfd_write path directly dereferences a misaligned datamatch value after an emulated store crosses a page boundary, causing BUG_ON to fire. Unprivileged code in a KVM guest with a datamatch-enabled ioeventfd is sufficient, and the resulting host failure interrupts co-resident virtual machines.

The record

CVE
CVE-2026-63806
Published
Jul 19, 2026
Updated
Jul 19, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-617, T1499.004
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 19, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 19, 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=2.6.32
  2. Affected versionversion=d34e6b175e61821026893ec5298cc8e7558df43a <5c87b47374682f69686068ad0a7779365a527b1c
  3. Affected versionversion=d34e6b175e61821026893ec5298cc8e7558df43a <5da9b1a87ec7cc3489c27016313524769f12d9e0
  4. Affected versionversion=d34e6b175e61821026893ec5298cc8e7558df43a <bf89e3738480d33cd515b4a18900e8443d40cd2e
  5. Affected versionversion=d34e6b175e61821026893ec5298cc8e7558df43a <f1edbed787ba67988ed34e0132ca128b052b6ce8

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=2.6.32; version=d34e6b175e61821026893ec5298cc8e7558df43a <5c87b47374682f69686068ad0a7779365a527b1c; version=d34e6b175e61821026893ec5298cc8e7558df43a <5da9b1a87ec7cc3489c27016313524769f12d9e0; version=d34e6b175e61821026893ec5298cc8e7558df43a <bf89e3738480d33cd515b4a18900e8443d40cd2e; version=d34e6b175e61821026893ec5298cc8e7558df43a <f1edbed787ba67988ed34e0132ca128b052b6ce8

Published CVSS scores

7.1kernel.orgCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/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.

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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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-617Reachable Assertion
T1499.004Endpoint Denial of Service: Application or System Exploitation

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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