CVE-2025-4421

SMM code execution via unchecked RSI pointer

Published Jul 30, 2025 · Updated Aug 14, 2025

Out-of-bounds write in InsydeH2O before Lenovo feature L05.05.40.011803.172079 allows local users to execute code in SMM. Callback7 reads an RSI-supplied pointer from CPU save state without validating the destination, then writes a fixed 64-bit value through it. Exploitation requires high local privileges and elevates execution from ring 0 to SMM, enabling firmware-resident code beneath the host operating system.

CVSS severity8.2
High
EPSS probability0.26%
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 write in InsydeH2O before Lenovo feature L05.05.40.011803.172079 allows local users to execute code in SMM. Callback7 reads an RSI-supplied pointer from CPU save state without validating the destination, then writes a fixed 64-bit value through it. Exploitation requires high local privileges and elevates execution from ring 0 to SMM, enabling firmware-resident code beneath the host operating system.

The record

CVE
CVE-2025-4421
Published
Jul 30, 2025
Updated
Aug 14, 2025
Vendor
Insyde Software
Product
InsydeH2O UEFI BIOS
Classifications
CWE-787, T1068
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. Jul 30, 2025CVE publishedPublication date reported by the CVE source.
  2. Aug 14, 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=Feature developed for Lenovo <L05.05.40.011803.172079

What conditions does exploitation require?

Attack vectorlocal
Required privilegesadmin

What is affected?

Insyde Software · InsydeH2O UEFI BIOSversion=Feature developed for Lenovo <L05.05.40.011803.172079

Published CVSS scores

8.2Insyde SoftwareCVSS: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

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
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-787Out-of-bounds Write
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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