Windows CLFS and five exploits used by ransomware operators

This report analyzes design and implementation flaws in the Windows Common Log File System (CLFS) driver and BLF file format that have led to numerous elevation-of-privilege vulnerabilities, including multiple zero-days observed in ransomware attacks. It documents CLFS internals, block/record layout, symbol and context structures, and explains how malformed BLF data and overlapping/invalid offsets can be leveraged to inject malicious CLFS_CONTAINER_CONTEXT structures and hijack kernel control flow.