CVE-2021-27097

Verified-boot bypass via malformed FIT structure

Published Feb 17, 2021 · Updated Nov 3, 2025

Improper FIT validation in Das U-Boot before 2021.04-rc2 allows local users to subvert verified boot with a modified boot image. The fit_check_format path omits full libfdt structural validation, while fdt_find_regions accepts invalid trees with multiple root nodes or a named root. Exploitation requires a crafted FIT to reach a signature-verifying boot flow, where accepted content can control the code loaded at boot.

CVSS severity7.8
High
EPSS probability1.07%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper FIT validation in Das U-Boot before 2021.04-rc2 allows local users to subvert verified boot with a modified boot image. The fit_check_format path omits full libfdt structural validation, while fdt_find_regions accepts invalid trees with multiple root nodes or a named root. Exploitation requires a crafted FIT to reach a signature-verifying boot flow, where accepted content can control the code loaded at boot.

The record

CVE
CVE-2021-27097
Published
Feb 17, 2021
Updated
Nov 3, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
T1542.003
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 17, 2021CVE publishedPublication date reported by the CVE source.
  2. Nov 3, 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 vectorlocal
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

6.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/A:P
7.8MITRECVSS:3.1/AV:L/AC:L/PR:N/UI:R/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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1542.003Pre-OS Boot: Bootkit

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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