CVE-2021-3453

Persistent firmware modification via incomplete Boot Guard coverage

Published Jul 16, 2021 · Updated Dec 16, 2025

Protection mechanism failure in Lenovo BIOS allows physically proximate attackers to write to SPI flash storage on affected systems. Boot Guard's Initial Boot Block coverage omits some UEFI firmware modules, so their contents are not verified against the protected hash before execution. Physical access, or an existing BIOS write-protection bypass, is required to install a persistent firmware implant.

CVSS severity6.8
Medium
EPSS probability0.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Protection mechanism failure in Lenovo BIOS allows physically proximate attackers to write to SPI flash storage on affected systems. Boot Guard's Initial Boot Block coverage omits some UEFI firmware modules, so their contents are not verified against the protected hash before execution. Physical access, or an existing BIOS write-protection bypass, is required to install a persistent firmware implant.

The record

CVE
CVE-2021-3453
Published
Jul 16, 2021
Updated
Dec 16, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-693, T1542.001
Attack vector
physical
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 16, 2021CVE publishedPublication date reported by the CVE source.
  2. Dec 16, 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?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorphysical
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

6.8LenovoCVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorphysical
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-693Protection Mechanism Failure
T1542.001Pre-OS Boot: System Firmware

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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