Microsoft releases mitigations for a Windows NT LAN Manager exploit that forces remote Windows systems to reveal password hashes that can be easily cracked.
Microsoft was quick to respond with a fix to an attack dubbed “PetitPotam” that could force remote Windows systems to reveal password hashes that could then be easily cracked. To thwart an attack, Microsoft recommends system administrators stop using the now deprecated Windows NT LAN Manager (NTLM).
Security researcher Gilles Lionel first identified the bug on Thursday and also published proof-of-concept (PoC) exploit code to demonstrate the attack. The following day, Microsoft issued an advisory that included workaround mitigations to protect systems.
The PetitPotam bug is tied to the Windows operating system and the abuse of a remote access protocol called Encrypting File System Remote Protocol (MS-EFSRPC). The protocol is designed to allow Windows systems to access remote encrypted data stores, allowing for management of the data while enforcing access control policies.
The PetitPotam PoC is a form of manipulator-in-the-middle (MitM) attack against Microsoft’s NTLM authentication system. Next, an attacker uses the file-sharing protocol Server Message Block (SMB) to request access to a remote system’s MS-EFSRPC interface. According to Lionel, this forces the targeted computer to initiate an authentication procedure and share its authentication details via NTLM.