TLDR: Cysic halted its bridge after an attacker minted 10 million CYS tokens without backing on BNB Smart Chain. Cysic blacklisted the wallet about 76 minutes later, restricting 2.8 million C
Cysic suspended its cross-chain bridge after an attacker created 10 million unauthorized CYS tokens on BNB Smart Chain and moved reported proceeds to Ethereum. The October 17 breach exposed faulty authentication of bridge messages authorizing token issuance.
The mint occurred at 12:31:38 UTC, according to its October 18 incident report. Investigators traced the breach to unauthorized access to a bridge database. The attacker then exploited a message-processing vulnerability to submit fraudulent mint instructions without a corresponding asset transfer.
On-chain activity cited in initial reporting linked the incident to sales of 7.2 million tokens and approximately 306.6 ETH received on Ethereum. Those proceeds were valued near $727,000, although the foundation has not verified the complete transaction trail or final losses.
Cross-chain bridges use authenticated messages to recognize transfers between blockchains and release matching assets. In this case, fraudulent instructions caused the system to mint tokens that lacked a legitimate transfer backing them. The breach therefore centered on bridge message validation, rather than a breakdown in the underlying network’s consensus.
Cysic blacklisted the receiving address at 13:47:52 UTC, about 76 minutes after the mint. By that point, 2.8 million tokens remained in the blocked wallet. That was 28% of the issuance; the remaining 7.2 million, or 72%, had moved out. The project’s cross-chain bridge was suspended to prevent further unauthorized activity.
An external security firm is now examining bridge messages, permissions and asset records, while investigators trace affected addresses. The bridge remains closed without a reopening date, pending security review and validation.
The scale of the issuance matters beyond the reported transfer proceeds. Project tokenomics document a total supply of 1 billion tokens, used for governance, computing services and network incentives. The 10 million unauthorized units equaled 1% of that stated supply, raising questions about unrecovered circulation.
However, the amount transferred to Ethereum should not be treated as the confirmed financial loss. Although initial tracking attributed 306.6 ETH to the attacker, the foundation has yet to establish how much was ultimately retained. Similarly, the 2.8 million restricted tokens are a verified containment measure, not evidence of recovery.
Mainnet consensus, block production and transaction execution continued normally, and existing assets in users’ wallets were unaffected. Users have also been warned against fake compensation links, recovery pitches and requests for private keys. A follow-up report is expected to address verified losses, fund tracing and remediation.
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