YellowKey Bitlocker Bypass Vulnerability

YellowKey Bitlocker Bypass Vulnerability(github.com)

85 points by entuno 5 days ago | 20 comments

coopreme 5 days ago |

Seems like a backdoor.

rurban 23 hours ago |

Just a little help for the fellow TSA and FBI folks

protimewaster 5 days ago |

What's the data in the FsTx folder? Is it just some magic data that Windows looks for?

e12e 4 days ago | |

Looks like it triggers a debug modus which in turn replay filesystem transactions from transaction logs?

https://infosec.exchange/@wdormann/116565129854382214

jllyhill 5 days ago |

Does anyone know if the fix was shipped already? If it not a backdoor, of course.

pajko 4 days ago | |

It does not matter. Who's gonna stop them adding a new backdoor in a later Windows Update(TM) ? T this point they are not to be trusted at all.

ChocolateGod 4 days ago | | |

Microsoft doesn't need a back door, they can literally sign a new bootchain with the same certificate and install them on your computer.

This is a bug / vulnerability, not a back door.

majorchord 2 days ago | | |

"Who's going to stop <any OS or app> from inserting a backdoor at some random point in the future? They are not to be trusted at all."

https://en.wikipedia.org/wiki/Slippery_slope

msuser 4 days ago |

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.

jamescrowley 4 days ago | |

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.”

anonymars 4 days ago | |

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

e12e 4 days ago | |

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

fh67 4 days ago | |

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.

pajko 4 days ago | | |

"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...

msuser 4 days ago | | |

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.