CVE-2021-3972Public exploit

Secure Boot disablement via manufacturing NVRAM controls

Published Apr 22, 2022 · Updated Aug 3, 2024

Leftover debug code in Lenovo Notebook BIOS on various models allows local users with elevated privileges to disable UEFI Secure Boot. The ChgBootDxeHook and ChgBootSmm manufacturing drivers honor attacker-created ChgBootSecureBootDisable or ChgBootChangeLegacy NVRAM variables and change the setting after reboot. Administrative firmware-variable access is required; disabling Secure Boot permits unsigned code to run during startup.

CVSS severity6.7
Medium
EPSS probability3.00%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Leftover debug code in Lenovo Notebook BIOS on various models allows local users with elevated privileges to disable UEFI Secure Boot. The ChgBootDxeHook and ChgBootSmm manufacturing drivers honor attacker-created ChgBootSecureBootDisable or ChgBootChangeLegacy NVRAM variables and change the setting after reboot. Administrative firmware-variable access is required; disabling Secure Boot permits unsigned code to run during startup.

The record

CVE
CVE-2021-3972
Published
Apr 22, 2022
Updated
Aug 3, 2024
Vendor
Lenovo
Product
Notebook BIOS
Classifications
CWE-489, CAPEC-121, CAPEC-661, T1553.006
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. Apr 22, 2022CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record 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=various

What conditions does exploitation require?

Attack vectorlocal
Required privilegesadmin

What is affected?

Lenovo · Notebook BIOSversion=various

Published CVSS scores

6.7Lenovo Group Ltd.CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
4.6NIST NVDAV:L/AC:L/Au:N/C:P/I:P/A:P

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
Privilegesadmin
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-489Active Debug Code
CAPEC-121Exploit Non-Production Interfaces
CAPEC-661Root/Jailbreak Detection Evasion via Debugging
T1553.006Code Signing Policy Modification

Public exploit references

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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