CVE-2026-59886 is a denial-of-service vulnerability in the pyasn1 library's handling of ASN.1 REAL values. The issue arises when converting decoded REAL values with very large exponents to Python floats, causing excessive CPU and memory consumption. This can hang processes that print, log, or compare such values decoded from untrusted ASN.1 data. The vulnerability affects pyasn1.type.univ.Real conversions triggered by BER, CER, and DER decoders. It was fixed in pyasn1 version 5.31.1_1.