Multiple denial-of-service vulnerabilities exist in the python-pyasn1 library prior to version 0.6.5. These flaws involve quadratic CPU time complexity during decoding of specially crafted ASN.1 data with long tag IDs, fragmented constructed strings, BIT STRINGs, and binary REAL values. An attacker can exploit these issues by sending malicious BER, CER, or DER encoded inputs to exhaust CPU resources and reduce service availability. No confidentiality or integrity impacts are reported. The issues are fixed in version 0.6.5.