Zero‑Day SignDrop Exploit Escalates to SYSTEM and Bypasses Windows Defender

What happened

Researcher Chaotic Eclipse released a PoC for SignDrop, a local‑privilege‑escalation bug in the CLFS driver that can be leveraged to force Windows Defender to create a signed file with SYSTEM privileges, effectively bypassing antimalware tamper‑protection.

Why it matters for trust and compliance

• The issue underscores the need for robust privileged‑access management and continuous monitoring of mitigation settings to maintain audit‑ready control assurance.
• Validate and document the configuration of CLFS authentication as part of privileged‑access control evidence.
• Monitor for anomalous antimalware process activity to provide defensible evidence of control effectiveness.

Who is affected

Recommended actions

1. Check the CLFS authentication mode registry key and ensure it is set to 2 or 3.
2. Apply Microsoft’s upcoming patch promptly and track security advisories.
3. Enforce least‑privilege policies and audit elevation‑of‑privilege events.
4. Deploy endpoint monitoring for suspicious calls to ServerMpUpdateEngineSignature.