Core

Syscoin

Syscoin’s team has recovered and destroyed 5 billion SYS tokens that an attacker minted through a flaw in the project’s cross-chain bridge.&nbsp;
Syscoin had to burn the minted tokens to restore its supply to its pre-exploit levels; however, its bridge remains offline.
<h3 id="span-how-did-the-exploit-happen-span">How did the exploit happen?</h3>
The <a href="https://syscoin.org/news/technical-postmortem-syscoin-bridge-incident-recovery-and-remediation" rel="noopener noreferrer nofollow">Syscoin team stated</a> that they detected the attack on June 7. The attack targeted a gap between how two layers of Syscoin’s infrastructure interpreted the same transaction data.&nbsp;
Syscoin runs a dual-chain architecture that consists of a Bitcoin-based UTXO chain and an Ethereum-compatible smart contract layer called NEVM. Both chains are connected by a bridge that verifies transaction proofs before moving tokens between them.
The project confirmed in a technical postmortem published June 15 that the attacker crafted a transaction containing two asset commitments that both pointed at the same output.&nbsp;
One commitment referenced native SYS, while the other referenced a custom test token the attacker had created.&nbsp;
Syscoin Core and the NEVM relay each parsed the ambiguous payload differently. Core treated the transaction as involving the custom token.&nbsp;
The relay read it as native SYS and instructed the vault contract to release 5 billion tokens.
The attacker had tested the approach first with a smaller probe transaction using a different custom token, according to the postmortem. The main exploit followed with a second custom asset.
<h3 id="span-how-was-the-syscoin-team-able-to-recover-the-exploited-fund-span">How was the Syscoin team able to recover the exploited fund?</h3>
After tracing the exploited funds across UTXO addresses, the <a href="https://www.cryptopolitan.com/syscoin-execs-100-million-tokens-fraud/" rel="noopener noreferrer nofollow">Syscoin team</a> contacted the attacker on-chain with a recovery address and a warning that exchange escalation and legal action would follow if the tokens were not returned.&nbsp;
The attacker sent the full 5 billion SYS back, according to on-chain records linked in the postmortem.
The team then destroyed the tokens. The burn transaction is publicly viewable on Syscoin’s block explorer.
On June 10, <a href="https://x.com/syscoin/status/2064828534196211967" rel="noopener noreferrer nofollow">Syscoin posted on X</a> that it had told exchanges they could safely reopen SYS deposits and withdrawals.
<h3 id="span-what-is-the-market-context-span">What is the market context?</h3>
The 5 billion minted tokens exceeded Syscoin’s legitimate circulating supply of roughly 891 million SYS by over 5 times, according to CoinMarketCap data.&nbsp;
Those minted tokens were worth around $9 million when the exploit happened.
SYS has struggled through most of 2026. CoinMarketCap lists the token at <a href="https://coinmarketcap.com/currencies/syscoin/" rel="noopener noreferrer nofollow">approximately $0.0026</a> with a market capitalization of $2.3 million. The token has declined by over 48% over the past 30 days and by over 91% in the past year.&nbsp;
<a href="https://defillama.com/chain/syscoin" rel="noopener noreferrer nofollow">DeFiLlama data</a> shows that Syscoin’s total value locked (TVL) in DeFi protocols had dropped to effectively zero, with only 14 active addresses and 73 transactions recorded over a 24-hour period before the incident.
<h3 id="span-what-has-the-syscoin-team-fixed-span">What has the Syscoin team fixed?</h3>
According to the Syscoin team, every bridge burn proof must map to exactly one asset identity, and both Core and the relay must agree on what that identity is.&nbsp;
The relay now rejects any burn transaction where asset commitments are duplicated, ambiguous, or could resolve inconsistently across layers. Core-side updates are also in progress to reject duplicate asset assignments at the consensus level.
The <a href="https://www.cryptopolitan.com/syscoin-bridge-paused-exploit-project/" rel="noopener noreferrer nofollow">bridge is still paused</a>, as the Syscoin team stated it is still pending final review. Native SYS deposits at exchanges have resumed, but cross-chain transfers through the bridge are closed until the team completes validation.
PeckShieldAlert data showed 14 major bridge and cross-chain exploits had drained a combined $340.7 million as of June 1, 2026. Around $28.62 million was lost in bridge-related exploits in May alone, the largest category by dollar amount that month.
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Syscoin recovers 5 billion SYS tokens after bridge exploit, burns them permanently

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