Cysic halts bridge after unauthorized mint of 10 million CYS on BNB Chain

Computing infrastructure project Cysic said an attacker breached its cross-chain bridge and minted 10 million of its CYS tokens without authorization. In an incident report posted on X on Oct. 18, the Cysic Foundation said the mint took place on BNB Smart Chain on Oct. 17, and that it had suspended the bridge and engaged an outside security firm to investigate. The 10 million tokens equal 1% of the 1 billion CYS total supply stated by the foundation.

1. Oct. 17, 21:31 KST10 million CYS minted without authorization to a single address on BNB Smart Chain
2. Oct. 17, 21:00-22:00 KSTCYS on Bithumb's Korean won market drops from 167 won to 138 won before closing the hour at 150 won (hourly candle)
3. Oct. 17, 22:47 KSTCysic blacklists the receiving address in the CYS token contract, blocking transfers
4. Oct. 18, 19:10 KSTCysic Foundation publishes its incident report
5. Oct. 18, 19:39 KSTCysic's official account says "The bridge remains suspended pending security review"

Unauthorized database access and a processing flaw enabled the mint

A cross-chain bridge moves tokens between separate blockchains. In a common design, tokens locked on one chain are matched by the same amount newly minted on the other. The foundation said preliminary findings indicate unauthorized access to a database supporting the bridge, and that the attacker exploited a flaw in the processing to mint the tokens. The full attack path and root cause remain under investigation.

The foundation said the incident was confined to the bridge's message processing and minting functions. "The incident did not result in the theft or unauthorized transfer of existing CYS or other assets held in user wallets," the report said. It added that the Cysic mainnet and other operational systems were not affected. The bridge has been closed to contain the risk, however, so cross-chain transfers through it are unavailable for now.

Cysic describes itself as a "ComputeFi" network that aims to turn computing hardware and resources such as GPUs and ASICs into tradable onchain assets. According to the foundation's tokenomics documentation, CYS began circulating with its token generation event (TGE) in the fourth quarter of 2025. Of the 1 billion total supply, 40.19% is allocated to ecosystem incentives, 23.62% to investors and 12.11% to contributors. Investor tokens are locked for 12 months and then unlock over 12 months. The CYS token contract on BNB Smart Chain currently records a supply of about 489.82 million tokens, including the unauthorized mint.

7.2 million tokens moved out in 76 minutes

According to the report, the unauthorized mint occurred at 9:31:38 p.m. KST on Oct. 17, and the foundation added the receiving address to the blacklist in the CYS token contract at 10:47:52 p.m., 1 hour and 16 minutes later. BNB Smart Chain records show the address now holds exactly 2.8 million CYS, meaning the other 7.2 million had already been moved elsewhere before the blacklist took effect.

The foundation said it is reviewing the subsequent transfers and swaps of the tokens and the actual losses, adding that the number of tokens minted does not by itself represent the final loss in U.S. dollar terms. U.S. crypto outlet The Defiant reported that onchain records show some tokens were sold before the blacklist took effect. The foundation said it is working with the security firm to trace the attack path and the flow of funds and will publish a follow-up report once the investigation is complete. No timeline has been set for reopening the bridge.

CYS slid as much as 17% on Bithumb's won market

In South Korea, CYS trades on Bithumb's Korean won market and on Upbit's BTC and USDT markets. Bithumb's hourly chart shows CYS fell about 17% from 167 won to 138 won during the 9 p.m. hour on Oct. 17, when the unauthorized mint occurred, before ending the hour at 150 won. CYS perpetual futures on Binance fell about 19% over the same hourly candle, from $0.1251 to $0.1013.

Prices have since partly recovered. Around 8:30 p.m. KST on Oct. 18, CYS traded at 159 won on Bithumb, with 24-hour trading value of about 4.18 billion won. Converting Bitget's price at the same time ($0.1175) at an exchange rate of 1,334.8 won per dollar gives about 157 won, putting Bithumb's price about 1.4% higher. As of the night of Oct. 18, Bithumb was processing CYS deposits and withdrawals normally and had not posted any notice designating CYS for trading caution.

The funding rate on Binance's perpetual futures (a payment exchanged between longs and shorts to keep futures in line with spot prices) stood near neutral at 0.005% on the night of Oct. 18, and open interest was about 26.79 million CYS.