On 23.11.2025, Cardano temporarily split into two chains after an attacker used an AI-generated script to exploit a known software bug.

Incident details

The incident saw newer nodes accept a malformed transaction while older nodes rejected it, producing a divergent, "poisoned" branch requiring urgent intervention.

Operators identified the anomaly quickly and applied an emergency patch to halt further chain divergence and to restore consensus across nodes.

Node operators coordinated rollback and chain reorganization steps where necessary to reconcile ledger states across participants.

Network response

As a precaution, exchanges and custodial services temporarily suspended deposits and withdrawals while validators coordinated the update and verified consistency.

Developers reported no user funds were lost as a result of the split, though trading and on-chain activity briefly slowed during remediation.

Attribution and market impact

Charles Hoskinson, Cardano co-founder, described the event as a targeted attack by a disgruntled stake-pool operator that affected all users.

A user known as "Homer J." claimed responsibility on social media, saying he acted alone and denied malicious intent despite network disruption.

The token's market price declined by more than 6 % following the incident, reflecting short-term market reaction to the operational disruption.

An internal investigation and community review are underway to determine exploit mechanics and to propose mitigations for similar AI-generated attack methods.