What happened
On June 7, 2026, Syscoin’s UTXO-to-NEVM bridge released 5 billion unauthorized SYS through a cross-layer interpretation mismatch; Syscoin reports the output was recovered and burned.
Technical root cause
Syscoin Core and the NEVM relay interpreted duplicate asset commitments targeting the same output index differently, allowing a malicious UTXO burn transaction to be accepted as a bridge release.
How it happened
The attacker submitted a UTXO burn transaction containing duplicate commitments for one output index. The differing Core and relay interpretations caused the bridge to release unauthorized SYS on the UTXO side.
Protocol details
Classification
Bridge & Cross-Chain
Protocol Type
DeFi Protocol
Category
Bridge Hack
Evidence
- report Post-mortem rekt.news
- report Syscoin Bridge incident postmortem syscoin.org
- analysis DeFiLlama defillama.com
Build your security review skills
Work through hands-on labs covering real exploit mechanics, review techniques, and defensive patterns.
