CVE-2026-48575: Secure Boot Security Feature Bypass Vulnerability

Synopsis

A protection mechanism failure in Windows Secure Boot allows a local, authenticated attacker to bypass the Secure Boot security feature entirely. The vulnerability is reached locally and requires an existing high-privilege account on the affected machine; no network exposure is needed. Successful exploitation lets an attacker load unsigned or tampered bootloaders and boot-level code, undermining the integrity guarantees Secure Boot is designed to enforce. Patched-image rebuilds at the 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 target is required.

• AuthenticationRequired

  An admin or otherwise privileged account on the local system is needed to trigger the bypass.

• Victim interactionNot required

  No action from another user or administrator is required once the attacker has local privileged access.

• Attack complexityDetail

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

Blast Radius

• Attacker loads an unsigned or tampered bootloader, bypassing Secure Boot's chain-of-trust validation at startup.
• Tampered boot-level code executes before the OS kernel, giving the attacker a position that persists across reboots and survives most OS-level defenses.
• Integrity assurances for measured boot and attestation flows are invalidated, because the Secure Boot chain can no longer be trusted as a root of trust.