CVE-2023-40546

Boot failure via malformed LogError invocation

Published Jan 29, 2024 · Updated Nov 20, 2025

NULL pointer dereference in Red Hat Shim allows local users to crash the UEFI bootloader while it creates an ESL variable. The error path in mok.c calls LogError() with arguments that do not match its format string, causing a read from address zero. Triggering requires local access and an ESL-variable creation failure; the fault interrupts boot, with no confidentiality or integrity impact reported.

CVSS severity6.2
Medium
EPSS probability0.44%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

NULL pointer dereference in Red Hat Shim allows local users to crash the UEFI bootloader while it creates an ESL variable. The error path in mok.c calls LogError() with arguments that do not match its format string, causing a read from address zero. Triggering requires local access and an ESL-variable creation failure; the fault interrupts boot, with no confidentiality or integrity impact reported.

The record

CVE
CVE-2023-40546
Published
Jan 29, 2024
Updated
Nov 20, 2025
Vendor
Red Hat
Product
Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support
Classifications
CWE-476, T1499.004
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 29, 2024CVE publishedPublication date reported by the CVE source.
  2. Nov 20, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Affected versions are unavailable in this record. Check the vendor advisory for version and patch details.

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Red Hat · Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update SupportAffected versions are unavailable in this record.
Red Hat · Red Hat Enterprise Linux 8Affected versions are unavailable in this record.
Red Hat · Red Hat Enterprise Linux 9.0 Extended Update SupportAffected versions are unavailable in this record.
Red Hat · Red Hat Enterprise Linux 7Affected versions are unavailable in this record.
Red Hat · Red Hat Enterprise Linux 9.2 Extended Update SupportAffected versions are unavailable in this record.
Red Hat · Red Hat Enterprise Linux 8.2 Advanced Update SupportAffected versions are unavailable in this record.
Red Hat · Red Hat Enterprise Linux 8.2 Telecommunications Update ServiceAffected versions are unavailable in this record.
Red Hat · Red Hat Enterprise Linux 8.2 Update Services for SAP SolutionsAffected versions are unavailable in this record.
Red Hat · Red Hat Enterprise Linux 9Affected versions are unavailable in this record.
Red Hat · Red Hat Enterprise Linux 8.4 Telecommunications Update ServiceAffected versions are unavailable in this record.
Red Hat · Red Hat Enterprise Linux 8.8 Extended Update SupportAffected versions are unavailable in this record.
Red Hat · Red Hat Enterprise Linux 8.6 Extended Update SupportAffected versions are unavailable in this record.
Red Hat · Red Hat Enterprise Linux 8.4 Update Services for SAP SolutionsAffected versions are unavailable in this record.

Published CVSS scores

5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
6.2Red HatCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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

CWE-476NULL Pointer Dereference
T1499.004Application or System Exploitation

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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