As far as I can tell, .NET doesn't have an ASN.1 parser for reading or writing data built in the framework. This means that any code that creates or verifies ASN.1 data is using a 3rd party library of varying quality. Bouncy Castle, and JavaScience for .NET are a few examples of such libraries.
I'm aware of a few production installations that use less widely used, and less tested ASN1 parsers. Considering the problems of parsing data in the past, and also that OpenSSL is still having ASN1 parsing issues I think that ASN1 parsing is a overlooked concern.
ASN.1 is used in TLS certificates, X.400 electronic mail, X.500 and Lightweight Directory Access Protocol (LDAP) directory services, H.323 (VoIP), Kerberos, BACnet and Simple network management protocol (SNMP) to describe the Protocol data units (PDU) they exchange. Any custom software that reads or writes ASN.1 data outside of a trusted wrapper could expose the system to risk.
How do I test and secure ASN.1 Parsers?
What parsers are more secure than others?
How does .NET do AD LDAP, Certificate oid validation, and kerberos without a built in library?