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 float conversions such as printing or comparisons. The issue is fixed in pyasn1 version 0.6.4, which handles large exponents safely. Applications that do not handle ASN.1 REAL values or avoid converting these values from untrusted sources are not affected.