This is a basic constraints extension, which is marked as critical.


$ openssl asn1parse -i < [EXTENSION]
    0:d=0  hl=2 l=  12 cons: SEQUENCE          
    2:d=1  hl=2 l=   3 prim:  OBJECT            :X509v3 Basic Constraints
    7:d=1  hl=2 l=   1 prim:  BOOLEAN           :255
   10:d=1  hl=2 l=   2 prim:  OCTET STRING      [HEX DUMP]:3000

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MAwGA1UdEwEB/wQCMAA=
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