CVE-2026-47656: Windows Boot Manager Security Feature Bypass Vulnerability

Synopsis

A protection mechanism failure (security feature bypass) in the Windows Boot Manager allows a local attacker with administrative privileges to circumvent boot-time security controls such as Secure Boot. The vulnerability is reached locally and requires no network exposure, but the attacker must already hold a high-privilege account on the target machine. Successful exploitation allows the attacker to undermine system integrity and confidentiality protections enforced at boot, enabling persistent tampering with the OS startup chain. Patched-image rebuilds at the applicable fix versions are available on HarborGuard for environments running affected Windows base images.

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-privileged account on the target system is required to exploit this vulnerability.

• Victim interactionNot required

  No victim interaction is needed; the attacker can carry out the exploit entirely on their own.

• Attack complexityDetail

  Attack complexity is low, meaning the exploit is reliable and does not depend on race conditions or special environmental factors.

Blast Radius

• Reads confidential data protected by boot-time security controls, including secrets or keys that Secure Boot is intended to guard.
• Modifies the OS boot chain by injecting unauthorized bootloader or early-startup code that persists across reboots.
• Bypasses platform integrity measurements, allowing the system to boot into a compromised state that appears legitimate to remote attestation checks.