Microsoft ASN.1 Library Length Integer Mishandling Memory Corruption Vulnerability

A vulnerability has been reported in the Microsoft ASN.1 library. This issue is related to insufficient checking of data supplied via an externally supplied length field in ASN.1 BER encoded data. This could result in an excessive value being used in a heap allocation routine, allowing for large amounts of heap memory to be corrupted. This could be leveraged to corrupt sensitive values in memory, resulting in execution of arbitrary code.

This vulnerability is exposed in a number of security related operating system components, including Kerberos (via UDP port 88), Microsoft IIS with SSL support enabled and NTLMv2 authentication (via TCP ports 135, 139 and 445). Other components may also be affected, though a comprehensive list is not available at this time.

It should be noted that because ASN.1 data will likely be encoded, for example Kerberos, SSL, IPSec or Base64 encoded, the malicious integer values may be obfuscated and as a result not easily detectable.


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