Microsoft Zero‑Day “YellowKey” Bypasses BitLocker Encryption, Prompting Immediate Mitigation
What Happened — Microsoft disclosed a critical Windows zero‑day, dubbed YellowKey, that can bypass BitLocker full‑disk encryption and grant attackers access to protected data. A temporary mitigation was released, but the vulnerability remains unpatched in many environments.
Why It Matters for TPRM —
- Encryption controls that were assumed “air‑gapped” can be subverted, exposing sensitive data.
- Third‑party risk assessments that rely on BitLocker compliance may be inaccurate.
- Regulatory obligations (e.g., GDPR, HIPAA) could be breached if encrypted data is exfiltrated.
Who Is Affected — Enterprises across all sectors that deploy Windows 10/11 with BitLocker enabled, especially those in finance, healthcare, and SaaS providers.
Recommended Actions —
- Deploy Microsoft’s temporary mitigation immediately on all affected endpoints.
- Conduct an inventory of BitLocker‑protected assets and verify encryption status.
- Re‑evaluate third‑party risk questionnaires to include this new attack vector.
- Accelerate patch management and monitor for any indicators of compromise related to YellowKey.
Technical Notes — The exploit leverages a kernel‑level vulnerability to inject code that disables BitLocker keys during the boot process. No public CVE number has been assigned yet; Microsoft’s advisory references internal tracking ID “MSRC‑2024‑XXXX”. Data at risk includes any files stored on encrypted volumes, potentially spanning personal, financial, and health records. Source: TechRepublic Security