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Windows 10 users: UPDATE NOW! Certificate validation is broken! (NSA: Critical Vulnerability Advisory issued)


Oct 25, 2017
Yes, but there are multiple versions (cumulative updates):

KB4528760 - Windows 10 v1903/v1909 and Windows Server v1903/v1909

KB4534273 - Windows 10 v1809 and Server 2019

KB4534293 - Windows 10 v1803 and Server 2016 v1803
Copying from the ETC thread: https://www.resetera.com/threads/windows-10-users-update-now-certificate-validation-is-broken-nsa-critical-vulnerability-advisory-issued.164843/

Duplicate post on Gaming because of how serious this is:

Microsoft's scheduled security update for Windows includes a fix to a potentially dangerous bug that would allow an attacker to spoof a certificate, making it look like it came from a trusted source. The vulnerability, reported to Microsoft by the National Security Agency, affects Windows 10, Windows Server 2016, Windows Server 2019, and Windows Server version 1803.

Microsoft has rated the update as "important" rather than critical. But in a blog post, Mechele Gruhn, the Principal Security Program Manager for Microsoft Security Response Center, explained that this was because "we have not seen it used in active attacks."

However, researchers outside Microsoft—including Google's Tavis Ormandy—have a much more dire assessment of the vulnerability and urge users to patch quickly before an active exploit appears.

The vulnerability is in the component of Windows' cryptography library that validates X.509 certificates, somehow bypassing the chain of trust used to validate the certificate. Microsoft's advisory on the vulnerability said that the bug could be used to fake the software-signing certificate on a malicious version of an application, making it look like it came from a trusted developer. However, the risk extends beyond just code-signing. A National Security Agency advisory indicates that the vulnerability could be used for man-in-the-middle attacks against secure HTTP (HTTPS) connections, as well, and to spoof signed files and emails.

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Oct 26, 2017
Well shit.
I am currently away from my computer, I hope nothing happens for the next 8 hours lol
But yeah, if app signing is broken, that's pretty bad.


Oct 25, 2017
Hamburg, Germany
I always have a hard time understanding all these security warnings. Why would this affect me, for instance?
Because some random asshole could send a nice virus to all PCs not having this security update, locking it up and/or destroying all data on it if you don't pay ONE MILLION DOLLARS to his bitcoin account, for example.

Like, similar to those things that happen all the freaking time still :D


Oct 25, 2017
For people who are still on version 1803 of Windows 10 the update you need is KB4534293 that is this months cumulative update file.


Oct 25, 2017
I've been avoiding updating because every time I update my screen gets really bright for some reason and my eye condition says "nope". Blaaah... I don't want to update...