EUVD-2026-35523
GHSA-4gp7-mp63-x473
Severity by source
AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:N
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:N
Lifecycle Timeline
3DescriptionCVE.org
Protection mechanism failure in Windows Secure Boot allows an authorized attacker to bypass a security feature locally.
AnalysisAI
Secure Boot bypass in Microsoft Windows allows an authorized local attacker with high privileges to defeat the platform's protection mechanism and tamper with the pre-OS boot chain. The CVSS 7.9 score reflects a scope-changing impact on confidentiality and integrity from a local vector, and no public exploit identified at time of analysis. The single MSRC reference indicates a Microsoft-tracked issue that primarily threatens code-integrity and boot-trust guarantees rather than runtime availability.
Technical ContextAI
Secure Boot is the UEFI firmware feature that validates the signatures of bootloaders, option ROMs, and early-OS components against a trusted key database (db/KEK/PK) before they are executed, anchoring the Windows trusted boot and measured boot chain. CWE-1329 (Reliance on a Component That is Not Updateable) points to a flaw where a fixed or non-updatable element of the boot trust chain - for example a hard-coded check, a signed component with revocable trust, or an embedded validation routine - can be leveraged to subvert verification. Because Secure Boot underpins downstream protections such as BitLocker measurements, VBS/HVCI, and Defender System Guard, a flaw here weakens the entire firmware-rooted trust hierarchy.
RemediationAI
Apply the Microsoft security update referenced in the MSRC advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-48573 to every affected Windows host, following the KB articles listed there for each Windows version (patch available per vendor advisory; exact fix build not enumerated in the provided inputs). Because Secure Boot fixes routinely require revoking previously trusted bootloaders, also deploy the corresponding DBX (Forbidden Signature Database) update and verify it took effect with Confirm-SecureBootUEFI and Get-SecureBootUEFI -Name dbx - be aware DBX revocations can render older recovery media, dual-boot Linux loaders, or unsigned vendor tools unbootable, so test before mass rollout. As compensating controls while patching is staged, restrict local administrator membership to reduce the population that can satisfy the PR:H prerequisite, enable BitLocker with TPM+PIN so that pre-boot tampering invalidates the key release, and turn on HVCI/Memory Integrity plus measured boot reporting (Defender for Endpoint attack surface telemetry or Intune attestation) to detect boot-chain anomalies; none of these stop the bypass itself but they raise the cost of weaponizing it.
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Same technique Authentication Bypass
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External POC / Exploit Code
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