CVE-2023-49721

Secure Boot bypass via enabled UEFI Shell

Published Feb 14, 2024 · Updated Oct 24, 2024

Secure Boot bypass in Canonical LXD allows guest OS users with root access to execute unsigned code through the VM firmware. LXD's OVMF build exposes the UEFI Shell as a built-in boot option under Secure Boot, and its mm command writes arbitrary physical memory. A guest root user can change the boot order, place an unattended startup.nsh on the EFI system partition, and gain system-level control after reboot.

CVSS severity6.7
Medium
EPSS probability0.24%
Next 30 days · Sep 17, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Secure Boot bypass in Canonical LXD allows guest OS users with root access to execute unsigned code through the VM firmware. LXD's OVMF build exposes the UEFI Shell as a built-in boot option under Secure Boot, and its mm command writes arbitrary physical memory. A guest root user can change the boot order, place an unattended startup.nsh on the EFI system partition, and gain system-level control after reboot.

The record

CVE
CVE-2023-49721
Published
Feb 14, 2024
Updated
Oct 24, 2024
Vendor
Canonical
Product
LXD
Classifications
CWE-276, T1542.003
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. Feb 14, 2024CVE publishedPublication date reported by the CVE source.
  2. Oct 24, 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=0
  2. Affected versionversion=0 <*

What conditions does exploitation require?

Attack vectorlocal
Required privilegesadmin

What is affected?

Canonical · LXDversion=0; version=0 <*

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 11, 2026Sep 17, 2026
Latest reporting daySep 17, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-276Incorrect Default Permissions
T1542.003Bootkit

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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