The pyasn1 library suffers from a Denial of Service vulnerability due to unbounded recursion when decoding ASN.1 data with deeply nested indefinite-length SEQUENCE or SET structures. An attacker can craft a payload that triggers recursive decoding calls without depth limits, causing the Python interpreter to crash with a RecursionError or exhaust memory, leading to service crashes or resource exhaustion. This affects services using pyasn1 for ASN.1 parsing such as LDAP, SNMP, Kerberos, and X.509 parsers. The vulnerability is fixed in pyasn1 versions 3.0.5 and 26.3.0_1.