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Comment by msuser | Hacker News Reader

How is this a backdoor if one of the steps is to reboot the system while holding down SHIFT? To boot in the first place, the drive needs to be unlocked.

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The EFI partition is unencrypted.

“you don't even need to plug an external storage device, you can just pull out the disk, copy the files in the EFI partition, put it back and it will still work. That's how bad it is.”

If you have physical access to plug in a flash drive, why would you need the drive unlocked to reboot into the recovery environment? Just power it off and trigger the boot options

Most users have it unlocked by TPM only as that is the default Microsoft configuration - you then reboot into windows recovery, yes if windows recovery is disabled or if bitlocker requires a startup pin then this is mitigated.

Point taken, but I would call this an authentication bypass (i.e. you can become administrator without any credentials) instead of a BitLocker bypass. It looks like at most, having BitLocker turned on is a requirement to trigger the bug/backdoor.

In any case I'd be very curious to read a response to these findings from someone at Microsoft.

"No, TPM+PIN does not help, the issue is still exploitable regardless, I asked myself this question, can it still work in a TPM+PIN environment ? Yes it does, I'm just not publishing the PoC, I think what's out there is already bad enough."

https://deadeclipse666.blogspot.com/2026/05/were-doing-silen...

Interesting. If TPM+PIN does not help, then what stands between Bitlocker and TPM unsealing the key?

In addition to sibling comments, the author claims it also affects tpm+pin.

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