CVE-2026-48568

What it actually does

This vulnerability is a local Windows Secure Boot protection mechanism failure. An attacker who already has high local privileges can bypass the Secure Boot trust boundary, allowing untrusted or tampered boot components to run despite Secure Boot being expected to enforce trusted startup. Successful exploitation can undermine boot-chain integrity and may enable stealthy persistence below the operating system, interference with platform security assumptions, or loading of code that Windows security controls would normally prevent. The CVSS vector indicates local access, low attack complexity, high required privileges, no user interaction, changed scope, and high confidentiality and integrity impact with no direct availability impact.

Why it matters to the business

If exploited, this flaw can weaken a core platform security control used to protect Windows workstations and servers during startup. The main business risk is that an attacker who has already obtained administrative or equivalent local control could make a compromised system harder to trust, harder to investigate, and more difficult to fully remediate because malicious changes may occur before the operating system and endpoint security tooling are fully active. The issue affects many supported Windows client and server versions, including Windows 10, Windows 11, Windows Server 2012, 2016, 2019, 2022, and 2025. Although EPSS is currently low, the impact is significant for high-value endpoints, domain administration workstations, virtualization hosts, servers handling sensitive data, and systems that rely on Secure Boot for compliance or measured-boot assurances.

How an attack unfolds

An attacker would first need to gain authorized local access with high privileges, such as local administrator, SYSTEM, or equivalent capability to modify boot-related configuration, EFI System Partition contents, firmware variables, or related update state. The attacker then abuses the Secure Boot protection failure to cause Windows to accept or execute boot components that should not be trusted under normal Secure Boot enforcement. After the bypass, the attacker may alter boot configuration, introduce a malicious or vulnerable boot component, or prepare persistence that executes before normal Windows security controls start. The result is not usually initial access by itself; rather, it is a post-compromise privilege-preservation and defense-evasion technique that can allow the attacker to maintain control, hide activity, or undermine forensic confidence in the affected device.

How to fix it

Apply the relevant Microsoft security updates for all affected Windows versions as soon as they are available through Windows Update, Microsoft Update Catalog, WSUS, Microsoft Configuration Manager, or the organization’s normal patch-management platform. Because Secure Boot issues may involve boot components, revocation state, or firmware trust material, follow Microsoft’s advisory and deployment sequencing carefully, including any required servicing stack updates, cumulative updates, Secure Boot DB/DBX updates, firmware or UEFI updates from OEMs, and staged revocation enforcement steps. Prioritize high-value systems, servers, administrative workstations, and devices where Secure Boot, BitLocker, virtualization-based security, device health attestation, or compliance baselines depend on boot-chain integrity. Where immediate patching is not possible, reduce risk by restricting local administrative access, enforcing least privilege, monitoring boot configuration and EFI System Partition changes, enabling BitLocker with TPM protection where appropriate, limiting physical access, and ensuring endpoint detection coverage includes tamper and boot-configuration monitoring.

How to confirm the fix worked

Confirm the operating system build includes the Microsoft security update that remediates this issue for the installed Windows version. Verify Secure Boot remains enabled after patching using System Information, PowerShell Confirm-SecureBootUEFI, firmware settings, or enterprise device compliance telemetry. Validate that boot configuration has not been unexpectedly altered by reviewing bcdedit output and comparing it to a known-good baseline. Inspect the EFI System Partition for unexpected files, recent modifications, or replaced bootloaders. Where applicable, confirm firmware, UEFI trust databases, and Secure Boot DBX revocation updates are current according to Microsoft and OEM guidance. For critical assets, perform a controlled reboot after patching to verify normal startup, BitLocker recovery behavior, Secure Boot state, and endpoint security sensor health.

Typical attack path

1. Obtain high-privilege local access to an affected Windows client or server.
2. Confirm the system uses Secure Boot or relies on Secure Boot-backed platform integrity guarantees.
3. Access boot configuration, EFI System Partition contents, Secure Boot-related variables, or update state that normally should be protected.
4. Trigger the Secure Boot protection mechanism failure to bypass expected validation of the boot chain.
5. Install or stage untrusted, tampered, or otherwise unauthorized boot components or configuration changes.
6. Reboot or otherwise force the system through the modified boot path.
7. Use the bypassed boot trust boundary for stealth, persistence, credential access support, or to weaken operating-system-level security controls.

How to detect it

There are no widely established public exploit indicators from the provided information, and the vulnerability is not listed in KEV. Detection should focus on evidence of Secure Boot bypass behavior and suspicious boot-chain modification. Collect and review Windows event logs related to boot, BitLocker, code integrity, Secure Boot, TPM, and firmware changes, including System, Security, Microsoft-Windows-CodeIntegrity/Operational, Microsoft-Windows-Kernel-Boot, Microsoft-Windows-BitLocker/BitLocker Management, Microsoft-Windows-TPM-WMI, and DeviceGuard/Operational where available. Look for unexpected Secure Boot disablement, boot configuration edits, BitLocker recovery events following configuration changes, new or modified files on the EFI System Partition, changes to boot manager paths, test-signing or integrity-check disabling, and use of administrative tools such as bcdedit, mountvol, diskpart, reagentc, bootsect, or firmware update utilities outside approved maintenance windows. Compare EFI System Partition contents and hashes against known-good baselines for the same OS version and patch level. Investigate systems where Secure Boot telemetry changes from enabled to disabled, where bootloaders have recent timestamps inconsistent with patch activity, or where local administrator activity precedes boot configuration changes. Because exploitation requires high local privileges, correlate these artifacts with privilege escalation, new admin accounts, suspicious remote management sessions, EDR tamper alerts, and abnormal interactive logons.

• Confirm-SecureBootUEFI : False
• Secure Boot is disabled
• bcdedit.exe /set
• bcdedit /set
• testsigning on
• nointegritychecks on
• bootstatuspolicy ignoreallfailures
• recoveryenabled no
• mountvol.exe /s
• mountvol /s
• \\EFI\\Microsoft\\Boot\\bootmgfw.efi
• \\EFI\\Boot\\bootx64.efi
• \\EFI\\Microsoft\\Boot\\BCD
• \\EFI\\Microsoft\\Boot\\bootmgr.efi
• Microsoft-Windows-CodeIntegrity/Operational
• Microsoft-Windows-Kernel-Boot
• Microsoft-Windows-BitLocker/BitLocker Management
• Microsoft-Windows-TPM-WMI
• DeviceGuard/Operational
• The Secure Boot update failed
• Secure Boot policy
• BitLocker recovery
• bootsect.exe
• diskpart.exe
• reagentc.exe

What your security team should do

• Prioritize patching on privileged-access workstations, domain administration systems, servers hosting sensitive workloads, and devices used for security administration.
• Inventory affected Windows versions across the estate and track remediation through OS build, cumulative update, and Secure Boot state rather than software inventory alone.
• Restrict and continuously review local administrator membership because exploitation requires high local privileges.
• Monitor for unauthorized changes to boot configuration, Secure Boot state, EFI System Partition contents, BitLocker protector state, and firmware settings.
• Treat suspicious boot-chain changes as high-severity post-compromise activity, even if no public exploit is currently known.
• For systems with abnormal Secure Boot or bootloader evidence, preserve forensic images of disk, EFI System Partition, event logs, and relevant firmware state before rebuilding.
• Use device compliance, EDR, and configuration-management tooling to alert when Secure Boot is disabled or when boot integrity settings deviate from baseline.
• Review Microsoft and OEM guidance for any required Secure Boot revocation or firmware update sequencing before broad deployment.