There has been lot of research to understand the Weaknesses in the Blockchain technology. Weekness of Bitcoin can also give an idea of possible weaknesses blockchain can have. Below are some of the weaknesses, please check link for full details.

  1. Might be a problem
    • Wallet Vulnerable To Theft
    • Tracing a coin's history
    • Sybil attack
    • Packet sniffing
    • Denial of Service (DoS) attacks
    • Illegal content in the block chain
  2. Probably not a problem
    • Breaking the cryptography
    • Scalability
    • Attacking all users
    • Dropping transactions
    • Attacker has a lot of computing power
    • Spamming transactions
    • The Finney attack
    • Rival/malicious client code
  3. Definitely not a problem
    • Generating tons of addresses
    • Everyone calculates at the same rate