ByeIntegrity 2.0 — Windows UAC Bypass

The second attack to bypass User Account Control (UAC) and gain elevated (Administrator) privileges to run any program at a high integrity level.

Requirements

• Administrator account
• UAC notification level set to default or lower

How it works

Unlike ByeIntegrity 1.0, ByeIntegrity 2.0 uses a completely different attack method — an elevated COM interface. The registry key HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\UAC\COMAutoApprovalList contains a list of CLSIDs that tell UAC to not prompt for elevation when creating an interface from any of the listed CLSIDs.

The CLSID {BDB57FF2-79B9-4205-9447-F5FE85F37312} represents the Internet Explorer Add-on Installer coclass — this is what ByeIntegrity 2.0 uses for its attack. The coclass allows two interfaces to be created:

• IID_IeAxiAdminInstaller
• IID_IeAxiInstaller2

The various methods called from these interfaces used in this attack eventually end up as their corresponding call in the elevated DCOM server ieinstal.exe as these methods:

• CIEAdminBrokerObject::InitializeAdminInstaller()
• CIEAdminBrokerObject::VerifyFile()
• CIEAdminBrokerObject::RunSetupCommand()

ByeIntegrity 2.0 uses these methods to launch cmd.exe as a child process of the elevated ieinstal.exe; creating an elevated instance of cmd.exe, therefore bypassing UAC.

How was this discovered?

The registry key COMAutoApprovalList contains lots of CLSIDs for actions that require elevated permissions but should not prompt because of the current UAC setting (if the setting is lower than the maximum value). I found the Internet Explorer Add-on Installer coclass to be particularly interesting, and while browsing the symbols, I found CIEAdminBrokerObject::RunSetupCommand(), which seemed like it would do what I wanted.

I spend lots of time reverse engineering the COM interfaces and the DCOM server to figure out how to use the interfaces and how they behave. Eventually, I figured out that using the three methods listed above allows us to execute an arbitrary program via a call to CreateProcessW() from the elevated DCOM server ieinstal.exe.

UACMe

This attack is implemented in UACMe as method #64. Unlike ByeIntegrity 1.0, this attack's code is the same as the code/implementation in UACMe. The only differences are that ByeIntegrity 2.0 uses cmd.exe as a lolbin whereas UACMe uses the Fubuki payload, and ByeIntegrity 2.0 uses bdeunlock.exe as the verification file, whereas UACMe uses consent.exe.

Using the code

If you’re reading this then you probably know how to compile the source. Just note that this hasn’t been tested or designed with x86 in mind at all, and it probably won’t work on x86 anyways.

Just like UACMe, I will never upload compiled binaries to this repo. There are always people who want the world to crash and burn, and I'm not going to provide an easy route for them to run this on somebody else's computer and cause intentional damage. I also don't want script-kiddies to use this attack without understanding what it does and the damage it can cause.

The undocumented methods/interfaces have been documented using comments. To read the documentation without reading the comment syntax, just hover over them in Visual Studio and read the tooltip that follows.

Example:

Supported versions

This attack works from Windows 7 (7600) up until the latest version of Windows 10.