The Microsoft Windows CryptoAPI, which is provided by Crypt32.dll , fails to validate ECC certificates in a way that properly leverages the protections that ECC cryptography should provide. As a result, an attacker may be able to craft a certificate that appears to have the ability to be traced to a trusted root certificate authority. Any software, including third-party non-Microsoft software, that relies on the Windows CertGetCertificateChain() function to determine if an X.509 certificate can be traced to a trusted root CA may incorrectly determine the trustworthiness of a certificate chain.



Microsoft Windows versions that support certificates with ECC keys that specify parameters are affected. This includes Windows 10 as well as Windows Server 2016 and 2019. Windows 8.1 and prior, as well as the Server 2012 R2 and prior counterparts, do not support ECC keys with parameters. For this reason, such certificates that attempt to exploit this vulnerability are inherently untrusted by older Windows versions.