MZ Automation libiec61850 Out-of-bounds Read

The GOOSE parser contains an off-by-one boundary-handling flaw that can
be triggered by a single unauthenticated Layer-2 multicast frame on the
process bus. When specific GOOSE message fields are processed, the
parser advances its internal buffer position incorrectly, resulting in a
heap out-of-bounds read. On affected platforms, this condition reliably
terminates the subscriber process and causes a denial-of-service.