According to Microsoft’s security update guide, a spoofing vulnerability that utilizes the Crypt32.dll file can be used to control a machine at will.
As stated within the emergency bulletin:
A spoofing vulnerability exists in the way Windows CryptoAPI (Crypt32.dll) validates Elliptic Curve Cryptography (ECC) certificates.
An attacker could exploit the vulnerability by using a spoofed code-signing certificate to sign a malicious executable, making it appear the file was from a trusted, legitimate source. The user would have no way of knowing the file was malicious, because the digital signature would appear to be from a trusted provider.
A successful exploit could also allow the attacker to conduct man-in-the-middle attacks and decrypt confidential information on user connections to the affected software.
The security update addresses the vulnerability by ensuring that Windows CryptoAPI completely validates ECC certificates.
Good news is that Microsoft has already released a patch to close the loophole so make sure you take care of this ASAP!