CVE-2021-3843

Arbitrary code execution via EEPROM SMI input validation

Published Nov 12, 2021 · Updated Aug 3, 2024

Improper input validation in Lenovo ThinkPad BIOS allows local users with elevated privileges to execute arbitrary code through an EEPROM SMI function. The vendor identifies the locus as the SMI function that accesses EEPROM but does not disclose which input or validation check is defective. Exploitation requires local access and elevated privileges; successful use runs attacker-controlled code in the firmware context.

CVSS severity6.7
Medium
EPSS probability0.28%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in Lenovo ThinkPad BIOS allows local users with elevated privileges to execute arbitrary code through an EEPROM SMI function. The vendor identifies the locus as the SMI function that accesses EEPROM but does not disclose which input or validation check is defective. Exploitation requires local access and elevated privileges; successful use runs attacker-controlled code in the firmware context.

The record

CVE
CVE-2021-3843
Published
Nov 12, 2021
Updated
Aug 3, 2024
Vendor
Lenovo
Product
ThinkPad BIOS
Classifications
CWE-20, T1068
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. Nov 12, 2021CVE 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 · ThinkPad BIOSversion=various

Published CVSS scores

6.7LenovoCVSS:3.1/AV:L/AC:L/PR:H/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.

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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

CWE-20Improper Input Validation
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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