A vulnerability in pyasn1's univ.Real type causes excessive CPU and memory consumption when converting decoded REAL values with large exponents to Python floats. This can lead to denial of service when applications process untrusted ASN.1 data and perform operations like printing, logging, or comparing these values. The issue affects float conversion methods and is reachable via BER, CER, and DER decoders. It is fixed in pyasn1 version 0.20.0_1.