Cardano Network Chain Split from Malformed Transaction Exploit
A malformed delegation transaction exploited a code bug in the Cardano blockchain on November 21, 2025, causing a temporary network split. A staking pool operator named Homer J used AI-generated code to push the transaction, leading to network instability, price decline, and economic losses to users.
What happened
On November 21, 2025, the Cardano blockchain network experienced a temporary chain split when a malformed delegation transaction was processed. The transaction exploited an old code bug in an underlying software library, causing nodes running different software versions to disagree on transaction validity.
A staking pool operator known as Homer J used AI-generated code to push the transaction and accepted responsibility for causing the network partition. Charles Hoskinson, Cardano founder, described the incident as a premeditated attack by a disgruntled operator who spent months attempting to damage the reputation of developer Input/Output Global.
Reported impact
The chain split caused network instability and slowed block production. ADA fell more than 7% in price, and the cryptocurrency exchange Upbit temporarily suspended ADA deposits and withdrawals.
The incident raised concerns about orphaned transactions and potential ADA double-spends that caused economic damage to some users. The split disrupted all Cardano users and sparked debate within the community over whether the actions exposed critical bugs or constituted an attack.
Index analysis
The malformed delegation transaction was valid at the protocol level but contained a flaw that the validation code did not properly trap, allowing the transaction to continue processing and trigger the network partition.
Governance controls
Staking pool operators were directed to download the latest version of node software to fix the issue and reconstitute the split chain. Intersect, the Cardano ecosystem governance organization, published an incident report following the event.
The Federal Bureau of Investigation was contacted and opened an investigation into the incident, with Hoskinson stating the matter involved tampering with and damaging a digital network that impacts the lives and commerce of millions of people.
Classification
Sources and evidence
This record was researched and written by the Index, based on the following original reporting.