CVE-2025-21210: Windows BitLocker Vulnerability in Exploited in Randomization Attack

The Windows BitLocker encryption system has a critical vulnerability (CVE-2025-21210) that can be exploited by a novel randomization attack targeting the AES-XTS encryption mode. This vulnerability allows attackers with physical access to the device to manipulate encrypted data, potentially exposing sensitive information in plaintext on the disk. This discovery highlights the ongoing evolution of threats targeting full-disk encryption systems.

BitLocker, a prominent full-disk encryption tool for Microsoft Windows, employs the AES-XTS encryption standard to safeguard storage devices. Unlike its predecessor, AES-CBC, which is vulnerable to bit-flipping attacks that enable precise modifications of decrypted plaintext, AES-XTS introduces randomization into the plaintext when ciphertext is altered.

While theoretically, targeted manipulations of encrypted data are difficult due to the randomization introduced by AES-XTS, the vulnerability identified as CVE-2025-21210 demonstrates that even this robust encryption standard can be exploited under specific circumstances. This highlights the ongoing challenge of ensuring the security of data encryption systems in the face of evolving attack techniques.

Computer forensics expert Maxim Suhanov explains that the vulnerability leverages a design weakness in the way BitLocker manages crash dump configurations.

By corrupting a single registry key (HKLM\System\ControlSet001\Control\CrashControl), attackers can disable the dumpfve.sys crash dump filter driver.

As a result of this vulnerability, the Windows kernel is forced to write unencrypted hibernation images directly to the disk. These images often contain sensitive data residing in RAM, such as passwords, encryption keys, and personal information.

Attack Phases

The attack involves two key stages:

Identifying Target Locations: The attacker must determine the precise disk offsets corresponding to critical registry keys or data structures. This is achieved by observing changes in ciphertext across multiple states of the encrypted disk.

Randomizing Ciphertext Blocks: Once the target location is identified, the attacker corrupts specific ciphertext blocks. In AES-XTS mode, this randomizes the corresponding plaintext block without affecting others.

This vulnerability poses significant risks in scenarios where physical access to devices is possible. For example:

Corporate Espionage: This flaw could be exploited by an attacker on stolen laptops that are protected by BitLocker using only the Trusted Platform Module (TPM).

Data Recovery Abuse: Devices sent for repair or recycling may be vulnerable if adequate security measures are not implemented.

Despite requiring high technical expertise and physical access for exploitation, the potential impact is severe as it exposes sensitive data stored in RAM.