CVE-2023-48733

Secure Boot bypass via enabled UEFI Shell

Published Feb 14, 2024 · Updated May 8, 2025

Security feature bypass in Canonical Ubuntu EDK II before 2023.05-2ubuntu0.1 allows local users to bypass UEFI Secure Boot. Ubuntu's OVMF and AAVMF firmware exposes its built-in UEFI Shell while Secure Boot is active; shell scripting and the mm command permit writes to physical memory. High-privilege OS-resident local users can change the boot order, trigger an unattended shell script after reboot, place an unsigned payload in memory, and redirect execution to it.

CVSS severity6.7
Medium
EPSS probability0.26%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Security feature bypass in Canonical Ubuntu EDK II before 2023.05-2ubuntu0.1 allows local users to bypass UEFI Secure Boot. Ubuntu's OVMF and AAVMF firmware exposes its built-in UEFI Shell while Secure Boot is active; shell scripting and the mm command permit writes to physical memory. High-privilege OS-resident local users can change the boot order, trigger an unattended shell script after reboot, place an unsigned payload in memory, and redirect execution to it.

The record

CVE
CVE-2023-48733
Published
Feb 14, 2024
Updated
May 8, 2025
Vendor
Canonical
Product
Ubuntu EDK II
Classifications
CWE-1188, T1542.003
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. Feb 14, 2024CVE publishedPublication date reported by the CVE source.
  2. May 8, 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 <2023.05-2ubuntu0.1

What conditions does exploitation require?

Attack vectorlocal
Required privilegesadmin

What is affected?

Canonical · Ubuntu EDK IIversion=0 <2023.05-2ubuntu0.1

Published CVSS scores

6.7CanonicalCVSS: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

CWE-1188Initialization of a Resource with an Insecure Default
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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