CVE-2026-48573: Secure Boot Security Feature Bypass Vulnerability

Synopsis

A protection mechanism failure in Windows Secure Boot allows a local attacker with administrative privileges to bypass the Secure Boot security feature entirely. The vulnerability is reached locally and requires no network access, but the attacker must already hold a high-privilege account on the target system. Successful exploitation lets the attacker load unsigned or tampered boot components, undermining firmware-level integrity guarantees. Patched-image rebuilds at the applicable fix versions are available on HarborGuard for environments running affected Windows versions.

HarborGuard Coverage

Exploit Conditions

• Network reachabilityNot required

  The attacker needs an existing shell or process on the host; no network path to the service is required.

• AuthenticationRequired

  An administrative or otherwise high-privilege account on the local system is needed to reach the vulnerable boot mechanism.

• Victim interactionNot required

  No user interaction is required; the attacker can trigger the bypass entirely through their own session.

• Attack complexityDetail

  Attack complexity is low, meaning the exploit is reliable and does not depend on race conditions, specific memory layouts, or other unpredictable environmental factors.

Blast Radius

• Attacker loads unsigned or tampered bootloaders and kernel components, bypassing firmware integrity enforcement at startup.
• Secure Boot policy enforcement is nullified, allowing persistent pre-OS implants or rootkits to survive reboots undetected.
• Confidentiality impact is high: attacker gains access to secrets and data protected by policies that assume a trusted boot chain (for example, BitLocker-adjacent protections that rely on measured boot).
• Data integrity is compromised: the attacker can modify boot-time configuration and persisted security policy without triggering integrity checks.