EUVD-2026-43801
GHSA-vm4m-9p6f-gcg7
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
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).
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Lifecycle Timeline
2DescriptionCVE.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. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires local access to an affected Windows/Windows Server host and at least low-level privileges (CVSS PR:L), with no user interaction (UI:N); the attacker must be able to run code locally that manipulates or supplies a boot component which then passes the flawed Secure Boot validation. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 3.1 base score is 7.8 (High) with vector AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H - local attack vector, low complexity, low privileges required, no user interaction, and high confidentiality/integrity/availability impact once the boot trust chain is subverted. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker who has already gained low-privileged local code execution on a targeted workstation or server - for example via a prior phishing foothold or an insider - abuses the improperly implemented Secure Boot check to load a tampered or unsigned boot component that the firmware should have rejected. This establishes a bootkit-level foothold that survives OS reinstallation and can weaken BitLocker's integrity assumptions. … |
| Remediation | 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. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, identify all Windows 10, Windows 11, and Windows Server (2016-2025) systems using your asset management or SCCM tools. …
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External POC / Exploit Code
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