Value Overflow Incident

Bitcoin's Most Critical Bug

On August 15, 2010, a critical integer overflow vulnerability was exploited, creating over 184 billion BTC in a single transaction. This was the most serious security incident in Bitcoin's history and threatened the network's existence.

The bug was in the transaction validation code: an integer overflow caused the total output value to wrap around, allowing an attacker to create enormous amounts of Bitcoin out of thin air. The transaction created 184,467,440,737.09551616 BTC — vastly exceeding the 21 million cap.

Response and Fix

The vulnerability was discovered within hours by Satoshi Nakamoto and other developers. A new client version was released that patched the overflow. The community quickly coordinated a soft fork — orphaned the invalid block and all subsequent blocks, effectively rolling back the chain to before the exploit.

This is a good example of why Bitcoin needs to be handled carefully. The system is not yet battle-tested.

— Satoshi Nakamoto, August 2010