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

Critical Windows BitLocker Vulnerability Exposes Sensitive Data

A novel randomization attack has been discovered, targeting the AES-XTS encryption mode in Windows BitLocker. Identified as CVE-2025-21210, this vulnerability allows attackers with physical access to manipulate ciphertext blocks, writing sensitive data to disk in plaintext

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Understanding the Flaw

BitLocker, a widely used full-disk encryption tool, relies on AES-XTS for encrypting storage devices. However, CVE-2025-21210 exploits a design flaw in how BitLocker handles crash dump configurations. By corrupting a single registry key, attackers can disable the dumpfve.sys crash dump filter driver, forcing the Windows kernel to write unencrypted hibernation images directly to disk.

The Attack Phases

1. *Identifying Target Locations*: Attackers determine the precise disk offsets corresponding to critical registry keys or data structures.

2. *Randomizing Ciphertext Blocks*: Attackers corrupt specific ciphertext blocks, randomizing the corresponding plaintext block without affecting others.

Risks and Implications

This vulnerability poses significant risks in scenarios where physical access to devices is possible, such as:

- Corporate espionage

- Data recovery abuse

Fixes and Mitigations

Microsoft has released an updated version of the fvevol.sys driver, introducing a validation mechanism to prevent exploitation. Users are strongly advised to apply the security patch immediately and implement essential safeguards.

Best Practices

Organizations must remain vigilant and adopt comprehensive security practices to mitigate risks associated with physical access and cryptographic weaknesses.