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 that can hang processes. This affects pyasn1 versions >=3.1 <3.8.1 and >=6.0.0 <6.2.2_1. The vulnerability is fixed in versions 3.8.1 and 6.2.2_1.