Symbiosis Bridge Exploit Exposes Cross-Chain Risk Without Touching Bitcoin

The Symbiosis native Bitcoin bridge was shut down on Friday after an attacker exploited its BridgeV2 contract to mint a massive amount of unbacked synthetic BTC. The attack, which occurred on September 11 at 04:28 UTC, resulted in the creation of more than 2^62 syBTC on BNB Chain and Ethereum.

The attacker was able to extract only about $336,000 in real value from the massive synthetic mint, highlighting a significant gap between the potential losses and actual realized loss. The incident emphasizes that Bitcoin's security was not compromised, but rather its bridges are vulnerable to attacks.

Just days after the Liquid Network breach, which resulted in a loss of $320 million, this incident raises concerns about the safety of cross-chain infrastructure. Symbiosis revealed that it stopped BTC routing immediately after detecting evidence of the attack and continued to function other routing protocols.