What is the CVSS score of EUVD-2026-43801?

EUVD-2026-43801 has a CVSS 3.1 base score of 7.8 (High). CVSS vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. EPSS exploitation probability: 0.3%.

Which versions of Windows Secure Boot are affected by EUVD-2026-43801?

Windows Secure Boot vulnerability (CVE-2026-49783) on Windows 10, 11, and Server systems enables locally authenticated attackers to compromise the boot-integrity chain, creating pathways for rootkits…. A patch is available.

How to fix or mitigate EUVD-2026-43801?

Within 24 hours, identify all Windows 10, Windows 11, and Windows Server (2016-2025) systems using your asset management or SCCM tools. Within 7 days, obtain the Microsoft security update from Windows Update or the Microsoft Update Guide, validate the patch in a test environment to confirm boot and BitLocker functionality, and prepare for production deployment. Within 30 days, deploy the patch to all affected systems through your standard change control process, verify installation via compliance reporting, and conduct spot-check integrity verification on a sample of critical infrastructure.

Windows Secure Boot EUVD-2026-43801

| CVE-2026-49783 HIGH

Improperly Implemented Security Check for Standard (CWE-358)

2026-07-14 microsoft

GHSA-vm4m-9p6f-gcg7

Authentication Bypass Microsoft Windows Server 2016 Windows Server 2019 Windows Server 2022 Windows Server 2025 Windows 10 Version 1607 Windows 10 Version 1809 Windows 10 Version 21H2 Windows 10 Version 22H2 Windows Server 2016 Server Core Installation Windows Server 2019 Server Core Installation Windows 11 Version 24H2 Windows 11 Version 25H2 Windows 11 Version 26H1 Windows Server 2025 Server Core Installation

7.8

CVSS 3.1 · Vendor: microsoft

Temporal: 6.8

Severity by source

Vendor (microsoft) PRIMARY

7.8 HIGH

AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CIRCL (temporal)

6.8 MEDIUM

cvss

vuln.today AI

7.8 HIGH

Local attacker with low privileges bypasses Secure Boot without user interaction; boot-chain compromise yields high confidentiality, integrity, and availability impact on the same system (scope unchanged).

3.1 AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

4.0 AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Primary rating from Vendor (microsoft).

CVSS VectorVendor: microsoft

Attack Vector

Local

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Lifecycle Timeline

Analysis Generated

Jul 14, 2026 - 18:35 vuln.today

CVE Published

Jul 14, 2026 - 17:05 nvd

HIGH 7.8

DescriptionCVE.org

Improperly implemented security check for standard in Windows Secure Boot allows an authorized attacker to bypass a security feature locally.

AnalysisAI

Security feature bypass in Windows Secure Boot (CWE-358) allows a locally authenticated attacker on affected Windows 10, Windows 11, and Windows Server (2016 through 2025) systems to defeat the boot-integrity trust chain due to an improperly implemented standard security check. Because Secure Boot is the gate that blocks unsigned/tampered bootloaders and rootkits, a successful bypass can enable pre-OS persistence and undermine downstream protections such as BitLocker and Measured Boot. There is no public exploit identified at time of analysis and the CVE is not listed in CISA KEV; Microsoft has published a patch via its update guide.

Technical ContextAI

Secure Boot is a UEFI firmware feature that verifies the cryptographic signature of every component in the boot chain (firmware drivers, bootloader, OS loader) against keys held in the platform's UEFI variables (db/dbx/KEK/PK) before execution, preventing bootkits and unsigned code from loading. CWE-358 (Improperly Implemented Security Check for Standard) indicates the flaw is not a missing check but a check that deviates from the specified standard behavior - the validation logic exists but can be satisfied or circumvented in a way the specification does not intend, allowing an untrusted component to pass verification. The CPE data scopes this to Microsoft's own boot-path components across Windows 10 (1607, 1809, 21H2, 22H2), Windows 11 (24H2, 25H2, 26H1), and Windows Server 2016/2019/2022/2025 including Server Core installations, indicating a shared OS-level Secure Boot enforcement component rather than a third-party bootloader.

RemediationAI

Patch available per vendor advisory - apply the Microsoft security update for CVE-2026-49783 to every affected Windows 10, Windows 11, and Windows Server (including Server Core) build; the exact fixed KB/build per version is listed at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-49783. Note that Secure Boot fixes frequently require an accompanying dbx (revocation list) update or a two-stage enablement to avoid bricking dual-boot or older-media scenarios, so validate the advisory's deployment guidance before mass rollout. Until patched, reduce exposure by restricting local and low-privilege code execution on sensitive hosts (limit local admin/interactive logon, enforce application control such as WDAC/AppLocker), keep BitLocker enabled with TPM+PIN so that boot-chain tampering triggers recovery-key prompts, and monitor Measured Boot / TPM attestation logs for unexpected boot-component changes - accepting that these are detective/limiting controls, not a substitute for the fix.