Microsoft Defender BlueHammer Elevation of Privilege Vulnerability Exploit

This module exploits a Time-Of-Check Time-Of-Use (TOCTOU) race condition within the Windows Defender signature update mechanism to achieve arbitrary code execution with SYSTEM privileges. The exploit chain leverages Cloud Files oplocks and an EICAR synchronization trigger to purposefully freeze Windows Defender's I/O operations. During this paused state, the module uses NTFS directory junctions and Object Manager symbolic links to redirect Defender's file access from a legitimate signature update file to the locked SAM database within a Volume Shadow Copy (VSS). After reading the SAM hive into memory, the module performs offline AES/DES decryption to harvest local NTLM hashes. Finally, it uses the pass-the-hash technique to temporarily reset an administrator's password, creates a self-deleting Windows service, and injects an interactive SYSTEM-level agent directly into the target user's desktop session. The steps performed by the exploit are: Downloads the Windows Defender signature update and extracts the required files directly into memory to evade disk-based detection. Freezes Windows Defender's file input/output operations at a precise moment by chaining an EICAR test file trigger with Cloud Files oplocks. Captures the exact object namespace path of the temporary Volume Shadow Copy (VSS) generated during Defender's remediation workflow. Executes a TOCTOU race condition using an NTFS junction and Object Manager symlink to trick Defender into opening the locked SAM database instead of the signature file. Reads the SAM database contents into memory and utilizes offline AES and DES decryption to extract local NTLM hashes. Employs a pass-the-hash technique to temporarily alter an administrator password, registers a self-deleting service to achieve SYSTEM privileges, and injects a CORE Impact agent into the active user's desktop session.