NEWS - Easy Bitlocker bypass with just a flash drive and physical access

Let me get this right. If I give a hacker physical access to my computer and the hacker then loads his malware, he can then bypass BitLocker. If that's what I'm understanding, I'm not concerned.

@TraderGary sleeps with this PC wrapped in his arms. No one is getting past him!

Correct, @TraderGary. This person has a flair for the dramatic.

TraderGary said:

Let me get this right. If I give a hacker physical access to my computer and the hacker then loads his malware, he can then bypass BitLocker. If that's what I'm understanding, I'm not concerned.

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pseymour said:

Correct, @TraderGary. This person has a flair for the dramatic.

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I apologize you feel that way friend. This is not a sky falling thing, but it is important I feel. I am not trying to make microsoft bashing my whole thing, just keep seeing stuff that bothers me personally and sharing with all of you once I verify the sources are respectable.

So the whole point of bitlocker is to help prevent the laptops data or external drives from being read if stolen correct?

So if the laptop is stolen, than without any malware at all, simple files on a usb drive, restarting the pc into the windows recovery environment, will gain access to the files.

The whole point of bitlocker is to protect and safeguard your files if the machine is stolen.

So yes, I would say this is a major issue, especially in a corporate setting. Otherwise, why would you use bitlocker in the first place? What would be the point of using it if the intent is not to allow sensitive files to be accessed?

Ways to mitigate this (I believe) would be to not allow bitlocker to be auto unlocked with tpm and have a physical power on password to boot.

Laptops are exactly the scenario BitLocker is usually sold for: lost/stolen devices. Microsoft describes BitLocker as addressing data theft or exposure from “lost, stolen, or inappropriately decommissioned devices,” including attacks where someone runs tools against the device or moves the hard drive elsewhere.

BitLocker encryption is NOT mathematically broken, and you can't just put the drive in another computer. The TPM still matters; but this attack abuses the fact that the original laptop can automatically unlock itself during boot/recovery.

BitLocker encryption is fully protecting my SSD when removed from my computer and read in another machine. My understanding is that's the main purpose of BitLocker.

My computer is fully password protected from anyone else logging in.

Getting to Windows recovery requires being able to successfully log in to my computer. Anyone that has successfully logged in already has full access to anything on my computer. That's the way BitLocker works.

I'm not going to log in to my computer and then hand it to a hacker.

What am I not understanding?

TraderGary said:

Getting to Windows recovery requires being able to successfully log in to my computer

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That is not true.

The attack chain is short and requires no specialized knowledge beyond following these steps:

1. Prepare a USB drive

The attacker creates a folder at a specific path on the USB drive inside a directory called \System Volume Information\FsTx. This folder contains crafted files designed to trigger the vulnerable behavior when WinRE processes them.

2. Boot into WinRE

The attacker plugs the USB into the target machine and reboots it into the Windows Recovery Environment. This can be done by holding Shift while clicking Restart at the login screen, or by interrupting the boot sequence (like powering off the machine when trying to load windows for example)— methods that require a few seconds of physical access.

3. Hold CTRL — get a shell

Once in WinRE, holding the CTRL key spawns an unrestricted command shell. From here, the attacker can use tools like diskpart to mount the BitLocker-protected volume and access its contents.

If a USB drive is not an option, the FsTx folder can be written directly to the EFI system partition — the small partition that stores boot files on modern machines — removing the need for external storage entirely.

The whole process, once the USB is prepared, takes under two minutes on a physical machine.


This means the following:

1.) Blocking usb from being a bootable device does not stop this exploit as it uses WRE (Windows Recovery Environment)

2.) You don't need any password at all.

What you can do to help:

1.) Require a bitlocker unlock pin at boot to prevent part of this attack. Although the researcher claims they might have found a way around this as well.

2.) Disable windows recovery environment.

Set a power-on password in the BIOS. The attacker must defeat the BIOS password first in order to force a booting system to pick WinRE.

garlin said:

Set a power-on password in the BIOS. The attacker must defeat the BIOS password first in order to force a booting system to pick WinRE.

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Another good step yes, so long as the motherboard does not have an easy bios password bypass. If your system is newer should be less of an issue.
Manufactures were caught using the same test secure boot key so I am sure codes are out there for that as well.

I just tested it, and can confirm it works.

My configuration uses a passwordless Microsoft Account + TPM + BitLocker + Secure Boot.

You're saying that configuration can be easily compromised?

Let's take this in order:

1. I can shutdown your PC (from the Lock Screen since Windows gives you the onscreen icon for powering down). Or unplug your PC if it's a desktop.

2. Power on. Secure Boot only protects which signed Windows files are allowed to boot up. CA 2023-signed boot manager if you're up to date. We're using the normal boot files.

3. Boot manager's job is to run winload.efi (which actually loads Windows). One of the safety features is you must be able to mash the keys during bootup in order to get into Windows Recovery. Like if your normal Windows was damaged and you need to get into WinRE. The key mashing logic is hard coded into the boot sequence.

Remember Crowdstrike? Windows kept boot looping over and over (for Crowdstrike, it was a corrupted kernel driver). I'm supposed to be able to key mash to escape out of the normal boot sequence, and reach WinRE.

4. So you convinced Windows to enter Recovery Mode. WinRE doesn't have a password. There are no users, because WinRE is basically a fancier WinPE with extra features and tools tacked on.

5. Some parts of Windows are designed to ummmm read mounted drives, just in case you need to transfer data to them. This is the hole.

6. Now if you had a BIOS password to prevent people from randomly rebooting, or have a BitLocker configured to always ask for a PIN... the attacker is blocked. TPM stores the BitLocker key in a secure enclave in the TPM chip, but by default Windows doesn't nag you to always provide the PIN.

It's assumed as long as this drive and this TPM are together, and they don't go their separate ways or get disrupted... TPM will provide BitLocker the key to unlock the Windows volume and allow booting. If you're super paranoid, then configure BitLocker to always ask for a PIN or password at boot time.

When BitLocker sits there indefinitely waiting for the password, it functions effectively as a lock to prevent Windows from booting... and thus preventing anyone from trying to key mash their way into WinRE.

Well, in any case, if this means a stolen device can now be bypassed, Bitlocker is just useless and even more like an annoyance. All the problems people has had with this tech, only for it to be bypassed physically, which is supposedly the main feature this holds.

Better to keep Bitlocker and device encryption turned off for me, at least I can make advanced operations, like restoring backups without having to worry about potential problems.

Not that I recommend it, it's just me, after all... I prefer simplicity over annoyances lol

This Chaotic Eclipse guy has some sort of axe to grind with Microsoft.

"This is not the first time Chaotic Eclipse has disclosed unpatched vulnerabilities in Microsoft products, and the researcher previously suggested they are displeased with the tech giant’s handling of vulnerability reports."
Source: Security Week

TraderGary said:

My configuration uses a passwordless Microsoft Account + TPM + BitLocker + Secure Boot.

You're saying that configuration can be easily compromised?

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Yes, but in how I know it can be extracted is not part of this thread.

TraderGary said:

My configuration uses a passwordless Microsoft Account + TPM + BitLocker + Secure Boot.

You're saying that configuration can be easily compromised?

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Yes. As I outlined in my prior post, no password is needed. No account access is needed. As Steve Jobs says - it just works.

Attacker steals laptop, attacker inserts USB with the files on it, attacker boots computer, they either hold down the power button while windows boots a few times to get it to go into recovery environment, or they let it go to the lock screen and then hold shift. Click the power button and choose restart. Once the window recovery starts to load, they hold down the control key, which opens the shell, granting them full access.

That’s all there is to it. It’s bad because of how simple it is to do.

Feel free to try it yourself here:

There should be an immediate Microsoft response. Let's see what happens.

Careful what you wish for. Fixing this will probably result a new WinRE, which leads to new security policy changes so you can't use the old RE. And then everyone will be required to rebuild their USB recovery drives.

We might even see a W11 25H2 v3 ISO. While the MCT changes the ISO every month, the direct download ISO has the broken RE inside. MS has to purge that from the website once the hole's been fixed.

It's just another WinRE exploit like the ones from a year or two ago. Wake me up when it can be done from a WinRE not hosted on the target system. I use Bitlocker pre-boot authentication with a password on my non-TPM systems and TPM+USB key (Apricorn Aegis) for the others. No one's beaten that, and this guy's only notable claim is that he's beaten TPM+PIN, which he didn't publish.

barreleye said:

It's just another WinRE exploit like the ones from a year or two ago. Wake me up when it can be done from a WinRE not hosted on the target system. I use Bitlocker pre-boot authentication with a password on my non-TPM systems and TPM+USB key (Apricorn Aegis) for the others. No one's beaten that, and this guy's only notable claim is that he's beaten TPM+PIN, which he didn't publish.

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That's definitely a good way to handle this.

Most companies that I know still use the basic BitLocker auto unlock with tpm. So that's why I felt it was important. It's the trade-off between security and convenience. Helps prevent pins that are forgotten and an annoyed help desk.

Also to note, while there definitely have been others in the past I think this one is a lot easier to do. Making the attack surface more widespread

andrew129260 said:

Most companies that I know still use the basic BitLocker auto unlock with tpm. So that's why I felt it was important. It's the trade-off between security and convenience. Helps prevent pins that are forgotten and an annoyed help desk.

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I don't know the numbers, so that could very well be true. But TPM-only is one of the weakest ways to configure drive encryption; probably the only thing weaker is password only (no TPM). You might as well not encrypt at all.