CVE-2026-48573: Windows 10 1607 Auth Bypass Vulnerability

CVE-2026-48573 Overview

CVE-2026-48573 is a protection mechanism failure vulnerability in Windows Secure Boot. An authorized attacker with high privileges can bypass a security feature locally on affected Windows client and server systems. The flaw is tracked under CWE-1329 (Reliance on Component That is Not Updateable) and affects boot-time integrity guarantees enforced by Secure Boot.

Microsoft published the advisory through the Microsoft Security Response Center. The vulnerability impacts a wide range of supported Windows 10, Windows 11, and Windows Server releases, including Server 2025.

Critical Impact
A successful bypass undermines Secure Boot's trust chain, allowing an attacker with administrative access to load unsigned or tampered boot components and persist below the operating system.

Affected Products

Microsoft Windows 10 (1607, 1809, 21H2, 22H2) across x86, x64, and ARM64
Microsoft Windows 11 (23H2, 24H2, 25H2, 26H1) across x64 and ARM64
Microsoft Windows Server 2012, 2012 R2, 2016, 2019, 2022, and 2025

Discovery Timeline

2026-06-09 - CVE-2026-48573 published to the National Vulnerability Database
2026-06-10 - Last updated in NVD database
2026-06-11 - EPSS scoring data published

Technical Details for CVE-2026-48573

Vulnerability Analysis

The vulnerability resides in the Windows Secure Boot implementation, the firmware-enforced mechanism that validates boot components against trusted signatures before transferring execution to the operating system loader. A protection mechanism failure means the validation logic can be circumvented under specific conditions, defeating the guarantee that only authorized code runs during early boot.

The CVSS vector indicates a local attack path requiring high privileges and no user interaction. The scope is changed, meaning a successful exploit affects components beyond the initially compromised security authority, and the impact spans confidentiality and integrity of the boot chain. An attacker who already holds administrative rights can leverage the flaw to plant a bootkit or replace trusted boot artifacts.

Root Cause

The root cause is classified as [CWE-1329], a reliance on a component that cannot be updated or whose update path is incomplete. In the Secure Boot context, a static or revocation-deficient trust anchor allows an attacker to present a component the firmware still treats as valid even though it should be excluded from the trust chain.

Attack Vector

Exploitation requires local access and prior privilege escalation to an administrative context. The attacker writes to boot-related EFI variables, the EFI System Partition, or replaces a signed boot binary that the vulnerable validation logic accepts. After reboot, the manipulated component executes within the Secure Boot trust boundary. No verified proof-of-concept code or in-the-wild exploitation has been published for this CVE, and it is not listed in the CISA Known Exploited Vulnerabilities catalog.

No verified exploit code is publicly available for CVE-2026-48573.
See the Microsoft Security Response Center advisory for technical details:
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-48573

Detection Methods for CVE-2026-48573

Indicators of Compromise

Unexpected modifications to files on the EFI System Partition (\EFI\Microsoft\Boot\*), including bootmgfw.efi and bootmgr.efi
Changes to Secure Boot related UEFI variables such as db, dbx, KEK, and PK outside of vendor firmware updates
New or modified boot configuration data (BCD) entries pointing to non-standard loaders
Discrepancies between TPM PCR[0-7] measurements and known-good baselines for the platform

Detection Strategies

Enable and monitor Measured Boot logs and remote attestation via the TPM to detect deviations from a trusted boot baseline
Audit changes to the EFI System Partition using file integrity monitoring and Windows Defender Application Control policies
Correlate administrative actions that touch bcdedit.exe, mountvol.exe, or scripts mounting the ESP with subsequent reboot events
Use endpoint telemetry to identify privilege escalation chains that precede boot configuration changes

Monitoring Recommendations

Centralize boot integrity attestation results and alert on any platform that fails attestation after a reboot
Monitor Windows event logs for Secure Boot policy changes and unsigned driver load attempts during boot
Track firmware and DBX revocation list update deployments to confirm consistent application across the fleet
Baseline administrative workstations and servers separately, as the local high-privilege requirement makes privileged endpoints the primary risk surface

How to Mitigate CVE-2026-48573

Immediate Actions Required

Apply the security update referenced in the Microsoft Security Update CVE-2026-48573 advisory to all affected Windows and Windows Server systems
Verify Secure Boot is enabled in firmware and that the latest DBX revocation list has been applied after patching
Restrict and audit local administrator access, since exploitation requires high privileges on the target host
Validate boot integrity through TPM attestation after the update completes

Patch Information

Microsoft has released a security update addressing CVE-2026-48573. Refer to the Microsoft Security Response Center advisory for the specific KB articles and package versions applicable to each supported Windows 10, Windows 11, and Windows Server release. Apply the update through Windows Update, WSUS, or your enterprise patch management workflow.

Workarounds

Enforce least privilege and remove unnecessary local administrator rights to limit who can stage an exploit
Require BitLocker with TPM and PIN protectors so that offline tampering with boot components invalidates the recovery state
Deploy Windows Defender Application Control or HVCI policies to restrict which binaries can execute during and after boot
Use measured boot attestation as a gating control for access to sensitive resources from affected endpoints

bash

# Verify Secure Boot status and current DBX state on Windows
Confirm-SecureBootUEFI
Get-SecureBootPolicy

# Inspect the current UEFI signature database revocation list
[System.Text.Encoding]::ASCII.GetString((Get-SecureBootUEFI dbx).Bytes) | Out-File dbx_state.txt