I previously posted about breaking out of restrictive desktop environments to gain access to a CMD shell or acess to Powershell. However sometimes the environment is even tighter, for example with Citrix environments you may not even be on a desktop but simply have an application exposed to you.
I’ve written a few articles recently about methods of escalating privileges on Windows machines, such as through DLL Hijacking and Unquoted Service Paths, so here I’m continuing the series with Privilege Escalation through Insecure Service configurations. This one’s pretty simple issue really, generally speaking it’s simply a matter of altering the service so that it runs the executable and parameters you want it to, instead the default configuration allowing you to supply a command and privilege level for the execution. So you can simply run the add user command as local system and create your own local administrator account!
I posted earlier about Privilege Escalation through Unquoted Service Paths and how it’s now rare to be able to exploit this in the real world due to the protected nature of the C:\Program Files and C:\Windows directories. It’s still possible to exploit this vulnerability, but only when the service executable is installed outside of these protect directories which in my experience is rare. Writing that post though got me thinking about another method of privilege escalation which I think is a little more common to see – DLL Hijacking.
A couple of days ago I posted an article about the first steps an attacker would likely take to perform a desktop breakout attack. Where that post left off was at the point of looking for privilege escalation from domain user to local administrator.
During Penetration Tests I often gain access to a selection of domain user accounts on my path to compromising a domain admin account. This is often a requirement these days for enumerating domain policy and also it’s quite common to find standard user accounts that have access to interesting information, such as HR or Finance accounts with access to staff and payroll information or a user with VPN access. During the post-engagement meeting with clients they’re often shocked at how I could launch online brute-force attacks against accounts without locking them out.