Overview
- Security researcher Abdelhamid Naceri published a public proof‑of‑concept this week called SignDrop that claims a local, non‑privileged Windows user can gain SYSTEM privileges.
- SignDrop abuses how the Common Log File System driver creates a companion “.cnpf” authentication file when a privileged process later opens an attacker‑prepared log so the file is written with the privileged process’s security context.
- The published chain commonly coerces Windows Defender to open the crafted log by using its signature‑update interface and Windows Object Manager symbolic links so the .cnpf file is created as SYSTEM and can be written by the attacker.
- Independent teams compiled and tested the PoC and confirmed it can work but said it is unreliable for consistent operational use, and there are no public reports of in‑the‑wild exploitation so far.
- Microsoft has not issued an advisory, CVE, or patch as of the November updates cycle and the only immediate mitigation—disabling CLFS authentication—reintroduces older memory‑corruption risks so administrators are advised to check the CLFS Authentication registry key while awaiting a vendor fix.