This is a basic constraints extension, where the critical field (BOOLEAN) is 3.

This is not valid because BOOLEANs in DER-encoding should use an octet of
either all 0 bits or all 1 bits.


$ 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           :3
   10:d=1  hl=2 l=   2 prim:  OCTET STRING      [HEX DUMP]:3000
-----BEGIN EXTENSION-----
MAwGA1UdEwEBAwQCMAA=
-----END EXTENSION-----