CVE-2026-96222: Microsoft Security Advisory CVE-2026-96222 - .NET Spoofing Vulnerability

October 13, 2026 (updated October 19, 2026)

Microsoft is releasing this security advisory to provide information about a vulnerability in System.Security.Cryptography.Xml. This advisory also provides guidance on what developers can do to update their applications to remove this vulnerability.

KeyInfoX509Data can accept serialized certificate formats containing attacker-controlled chain metadata instead of requiring a plain X.509 certificate, contributing to certificate-forgery and token-spoofing paths.

References

Code Behaviors & Features

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