Cardano Blockchain Experiences ‘Split’ Due to Transaction Error

Perpetrator confessed, but Charles Hoskinson mentioned FBI involvement.

On November 21, a “malformed” transaction on the Cardano mainnet caused a technical failure, leading to a split in the blockchain’s history.

According to an incident report by Cardano Intersect, the issue stemmed from a fault in the core software library that was not caught by the validation code. Executing a delegation transaction led to a divergence in the blockchain, effectively splitting it into two separate chains — “poisoned” and “healthy.”

“The incident was made possible due to a specific deserialization hash error that arose in 2022. This feature was not used until last year. Due to the fault, a hash of excessive size in an incorrect delegation transaction could pass initial checks when it should have been rejected,” experts explained.

Analysts noted that a similar attack attempt on the Preview test network preceded the “deliberate anomaly.”

The network team has already released an emergency update. User funds remain unaffected.

Technically, the blockchain did not halt, but there was a significant gap between block productions.

Perpetrator Identified

The incident was claimed by a staking pool operator named Homer J. He stated that out of curiosity, he wanted to reproduce the failed transaction, consulting AI for this purpose.

Sorry (I know the word isn’t enough given the impact of my actions) Cardano folks, it was me who endangered the network with my careless action yesterday evening. It started off as a “let’s see if I can reproduce the bad transaction” personal challenge and then I was dumb enough

— Homer J (AAA) (@KpunToN00b) November 21, 2025

“I didn’t sell any ADA coins before my ‘production testing,’ didn’t short (I don’t even know how to), didn’t work with anyone on this, and didn’t plan [the attack] long and carefully. I have much to lose from my actions. Sorry, Cardano community, I truly regret it,” the user wrote.

While some supported Homer J, noting his help in identifying critical vulnerabilities, Cardano co-founder Charles Hoskinson called the incident a “premeditated attack by a disgruntled SPO who spent months seeking ways to harm the brand and reputation of IOG.”

There was a premeditated attack from a disgruntled SPO who spent months in the Fake Fred discord actively looking at ways to harm the brand and reputation of IOG. He targeted my personal pool and it resulted in disruption of the entire cardano network.

Every single user was…

— Charles Hoskinson (@IOHK_Charles) November 21, 2025

“He targeted my personal pool, which led to the failure of the entire Cardano network. Every user was affected. Validators are losing block rewards. Double spending is possible. DeFi disruptions. It will take weeks to fix this chaos, and even longer to restore brand and reputation damage,” the developer stated.

The responsible user apologized only because he was aware of an ongoing criminal investigation, the network co-founder added.

In a separate video address, Hoskinson stated that “the situation stirred up a hornet’s nest,” as such actions are considered serious crimes in many jurisdictions. According to the programmer, the FBI contacted him for additional information.

“The incident is an interference with and disruption of a digital network. Perhaps [those involved] thought it was just fun and games: ‘Oh, look, we broke Charles’s toy,'” he emphasized.

However, ADA prices barely reacted to the incident. In recent days, the coin’s trend has aligned with the overall market downturn.

“No one noticed the Cardano network split because no one uses the blockchain,” wrote one user.

Back in August, on-chain researcher ZachXBT described the blockchain’s operational model as an “insider enrichment scheme.”