CVE-2022-28735

Secure Boot bypass via permissive file verification

Published Jul 20, 2023 · Updated Feb 13, 2025

Improper verification in GNU GRUB before 2.06-3 allows local users to load unverified code through shim-powered Secure Boot. The shim_lock_verifier_init function initially marks every file to skip verification, letting TPM or OpenPGP verifiers approve modules, and restricts checks only for recognized kernel and chainloaded-image types. Privileged access to the GRUB environment on a shim-powered Secure Boot system is required; successful abuse breaks the boot trust chain and permits unverified modules or code to run.

CVSS severity6.7
Medium
EPSS probability0.31%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper verification in GNU GRUB before 2.06-3 allows local users to load unverified code through shim-powered Secure Boot. The shim_lock_verifier_init function initially marks every file to skip verification, letting TPM or OpenPGP verifiers approve modules, and restricts checks only for recognized kernel and chainloaded-image types. Privileged access to the GRUB environment on a shim-powered Secure Boot system is required; successful abuse breaks the boot trust chain and permits unverified modules or code to run.

The record

CVE
CVE-2022-28735
Published
Jul 20, 2023
Updated
Feb 13, 2025
Vendor
The GnuPG Project
Product
GNU GRUB
Classifications
T1542.003
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. Jul 20, 2023CVE publishedPublication date reported by the CVE source.
  2. Feb 13, 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=0 <2.06-3

What conditions does exploitation require?

Attack vectorlocal
Required privilegesadmin

What is affected?

The GnuPG Project · GNU GRUBversion=0 <2.06-3

Published CVSS scores

7.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
6.7GNU GRUB projectCVSS: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 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

T1542.003Bootkit

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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