CVE-2026-63807

Host crash via unchecked shadow-page GFN

Published Jul 19, 2026 · Updated Jul 19, 2026

Out-of-bounds read in Linux Kernel KVM's x86 shadow MMU allows guest OS users to crash the host via a crafted hugepage mapping. kvm_mmu_recover_huge_pages passes a parent shadow page's base GFN to kvm_mmu_max_mapping_level before confirming that the GFN belongs to the target memslot, causing an out-of-bounds lpage_info read. The path requires a guest PTE hugepage that extends below a memslot during hugepage recovery; the documented result is a host page fault and kernel oops.

CVSS severity8.8
High
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

Out-of-bounds read in Linux Kernel KVM's x86 shadow MMU allows guest OS users to crash the host via a crafted hugepage mapping. kvm_mmu_recover_huge_pages passes a parent shadow page's base GFN to kvm_mmu_max_mapping_level before confirming that the GFN belongs to the target memslot, causing an out-of-bounds lpage_info read. The path requires a guest PTE hugepage that extends below a memslot during hugepage recovery; the documented result is a host page fault and kernel oops.

The record

CVE
CVE-2026-63807
Published
Jul 19, 2026
Updated
Jul 19, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-125, T1499.004
Attack vector
local
Privileges
authenticated

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=5.12
  2. Affected versionversion=9eba50f8d7fcb61774f160890f98239fa3ab68a6 <18587f9831612e24cd8f24be1ec15478feff7abc
  3. Affected versionversion=9eba50f8d7fcb61774f160890f98239fa3ab68a6 <48b91ed7e22bb82571c34f8b80b6ecdc90a6fab8
  4. Affected versionversion=9eba50f8d7fcb61774f160890f98239fa3ab68a6 <5cab1c989f938f5e1b9a0de66486f1fc2c28479b
  5. Affected versionversion=9eba50f8d7fcb61774f160890f98239fa3ab68a6 <7b52008023b7facf40fba3ebe92449bda8ea53b9
  6. Affected versionversion=9eba50f8d7fcb61774f160890f98239fa3ab68a6 <b2ae3245ea44dccaa9af676b6747476951883318
  7. Affected versionversion=9eba50f8d7fcb61774f160890f98239fa3ab68a6 <c5c29b3c268332afe67d598a034c58344540ed92
  8. Affected versionversion=9eba50f8d7fcb61774f160890f98239fa3ab68a6 <ef057cbf825e03b63f6edf5980f96abf3c53089d

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=5.12; version=9eba50f8d7fcb61774f160890f98239fa3ab68a6 <18587f9831612e24cd8f24be1ec15478feff7abc; version=9eba50f8d7fcb61774f160890f98239fa3ab68a6 <48b91ed7e22bb82571c34f8b80b6ecdc90a6fab8; version=9eba50f8d7fcb61774f160890f98239fa3ab68a6 <5cab1c989f938f5e1b9a0de66486f1fc2c28479b; version=9eba50f8d7fcb61774f160890f98239fa3ab68a6 <7b52008023b7facf40fba3ebe92449bda8ea53b9; version=9eba50f8d7fcb61774f160890f98239fa3ab68a6 <b2ae3245ea44dccaa9af676b6747476951883318; version=9eba50f8d7fcb61774f160890f98239fa3ab68a6 <c5c29b3c268332afe67d598a034c58344540ed92; version=9eba50f8d7fcb61774f160890f98239fa3ab68a6 <ef057cbf825e03b63f6edf5980f96abf3c53089d

Published CVSS scores

8.8kernel.orgCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/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

CWE-125Out-of-bounds Read
T1499.004Application 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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