CVE-2026-77892 in Windows
Summary
by MITRE • 09/09/2026
No cwe for this issue in Windows Boot Manager allows an unauthorized attacker to elevate privileges with a physical attack.
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Analysis
by VulDB Data Team • 09/09/2026
The vulnerability described involves a critical security flaw within the Windows Boot Manager component of Microsoft Windows operating systems, which permits an unauthorized actor to escalate their privilege level through direct physical access to the target machine. This specific class of vulnerabilities falls under the domain of bootkit attacks or firmware-level exploitation, where the attacker bypasses traditional software-based defenses by intervening during the earliest stages of system initialization. The absence of a predefined Common Weakness Enumeration (CWE) identifier for this particular manifestation highlights its unique nature as a physical attack vector that exploits trust relationships established before the operating system fully loads and security controls are active.
In technical terms, the Windows Boot Manager is responsible for loading the bootloader and subsequently the kernel into memory during the startup process. If an attacker with physical access can manipulate hardware interfaces such as USB ports, PCIe slots, or external boot devices, they may be able to inject malicious code or alter boot configurations before the operating system's integrity checks are fully enforced. This allows the attacker to execute arbitrary code with SYSTEM-level privileges, effectively gaining complete control over the machine. The flaw likely stems from insufficient validation of boot sources or a lack of strict enforcement of secure boot policies that would otherwise prevent unsigned or unauthorized boot loaders from executing.
The operational impact of this vulnerability is severe, as it results in full system compromise without requiring any prior authentication on the operating system itself. An attacker can install persistent backdoors, exfiltrate sensitive data stored on disk, disable security software such as antivirus programs and firewalls, or use the compromised machine as a pivot point for further network attacks. Because this occurs at the pre-boot stage, traditional endpoint detection and response solutions are often unable to detect or mitigate the intrusion once it has taken root in memory during initialization. This makes remediation difficult after exploitation, necessitating complete reinstallation of the operating system from trusted media rather than simple patching.
Mitigation strategies for this type of physical attack vector primarily rely on hardware-based security features and strict access control policies. Enabling Secure Boot is a critical step, as it ensures that only signed boot loaders and kernels are allowed to execute, thereby preventing unauthorized code injection during the startup process. Additionally, configuring BIOS or UEFI firmware passwords can prevent attackers from changing boot order settings or disabling secure boot via hardware manipulation. Physical security measures such as locked server rooms, biometric access controls, and surveillance are essential to deny physical proximity to potential attackers. Organizations should also consider implementing full-disk encryption with pre-boot authentication, which ensures that even if an attacker gains physical access, they cannot read the data on the drive without proper credentials. Regularly updating firmware is also recommended to address known vulnerabilities in boot-related components.
From a threat intelligence perspective, this vulnerability aligns with MITRE ATT&CK techniques related to Bootkit execution and Pre-OS Boot Compromise. Attackers leveraging such flaws often operate within the context of advanced persistent threats or targeted espionage campaigns where physical access can be obtained through social engineering or insider threats. The lack of a specific CWE identifier suggests that this may be an implementation-specific flaw rather than a generic coding error, emphasizing the need for defense-in-depth strategies that combine hardware security features with rigorous physical access controls to protect against such sophisticated attack vectors.