CVE-2025-40266

Hypervisor compromise via unchecked FF-A offset

Published Dec 4, 2025 · Updated Aug 5, 2026

Out-of-bounds access in Linux KVM arm64 allows local users with host-kernel control to compromise the EL2 hypervisor through FF-A sharing. In __do_ffa_mem_xfer, adding the host-supplied composite offset to the region-header size can wrap a 32-bit value before buffer-bound and pointer calculations. Reaching the flaw requires code execution in the host kernel and protected KVM with FF-A proxying; exploitation can disclose hypervisor memory, corrupt page ownership, or panic the host and its guests.

CVSS severity8.2
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

Out-of-bounds access in Linux KVM arm64 allows local users with host-kernel control to compromise the EL2 hypervisor through FF-A sharing. In __do_ffa_mem_xfer, adding the host-supplied composite offset to the region-header size can wrap a 32-bit value before buffer-bound and pointer calculations. Reaching the flaw requires code execution in the host kernel and protected KVM with FF-A proxying; exploitation can disclose hypervisor memory, corrupt page ownership, or panic the host and its guests.

The record

CVE
CVE-2025-40266
Published
Dec 4, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1068
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. Dec 4, 2025CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 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=3.11
  2. Affected versionversion=6211753fdfd05af9e08f54c8d0ba3ee516034878 <103e17aac09cdd358133f9e00998b75d6c1f1518
  3. Affected versionversion=6211753fdfd05af9e08f54c8d0ba3ee516034878 <bc1909ef38788f2ee3d8011d70bf029948433051
  4. Affected versionversion=6211753fdfd05af9e08f54c8d0ba3ee516034878 <f9f1aed6c8a3427900da3121e1868124854569c3
  5. Affected versionversion=6211753fdfd05af9e08f54c8d0ba3ee516034878 <fc3139d9f4c1fe1c7d5f25f99676bd8e9c6a1041

What conditions does exploitation require?

Attack vectorlocal
Required privilegesadmin

What is affected?

The Linux Kernel Organization · Linuxversion=3.11; version=6211753fdfd05af9e08f54c8d0ba3ee516034878 <103e17aac09cdd358133f9e00998b75d6c1f1518; version=6211753fdfd05af9e08f54c8d0ba3ee516034878 <bc1909ef38788f2ee3d8011d70bf029948433051; version=6211753fdfd05af9e08f54c8d0ba3ee516034878 <f9f1aed6c8a3427900da3121e1868124854569c3; version=6211753fdfd05af9e08f54c8d0ba3ee516034878 <fc3139d9f4c1fe1c7d5f25f99676bd8e9c6a1041

Published CVSS scores

8.2Linux kernel CNACVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1068Exploitation for Privilege Escalation

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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