Cysic Halts Bridge After Exploit Moves $727,000 to Ethereum

Cysic has suspended its cross-chain bridge after an attacker exploited it to mint 10 million unauthorized CYS tokens on BNB Chain, according to The Block. The outlet, citing onchain records, reports the attacker sold 7.2 million of those tokens and bridged roughly $727,000 in proceeds, equal to about 306.6 ETH, to Ethereum before the project could respond. Traders should treat the CYS token with caution given the unresolved exploit.

The Block reports the fraudulent mint occurred at 8:31 a.m. ET on Saturday, with the attacker moving tokens out five minutes later across 26 transfers in 15 transactions, completed by 8:59 a.m. ET. Twelve of those fifteen transactions were routed through OKX's decentralized exchange aggregator, the outlet says, and the attacker converted proceeds to ETH using cross-chain services including SWFT, Mayan and deBridge, receiving payouts of 40.88 ETH, about 224.66 ETH and 41.05 ETH, respectively. The combined ETH was then moved to a second wallet in five transfers by 9:11 a.m. ET, per Etherscan records cited by The Block.

Cysic blacklisted the attacker's address in the CYS token contract at 9:47 a.m. ET, freezing the remaining 2.8 million unauthorized tokens, The Block reports, citing onchain data and the Cysic Foundation's incident report. The outlet notes the freeze came roughly 76 minutes after the attacker's first move and about 48 minutes after transfers stopped. Cysic said the attacker gained unauthorized database access and exploited a flaw in message-processing logic to submit a fraudulent mint, adding that existing user assets were not stolen. The company, founded in 2022 and backed by a $6 million seed round led by Polychain Capital in 2023, has engaged a security firm and will keep the bridge closed pending review. The attacker's identity and the security firm remain unknown.