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 tags. An attacker can craft a payload that causes the decoder to recurse excessively, leading to a RecursionError or out-of-memory crash, terminating the service process. This affects services parsing untrusted ASN.1 data such as LDAP, SNMP, Kerberos, or X.509 parsers. The vulnerability is fixed in pyasn1 versions 0.8.03 and 3.0.7_7.