Cardano network faced unexpected disruption on November 21 when a developer’s flawed test triggered the blockchain’s first major chain split in eight years.
The event exposed an old software vulnerability and prompted a strong response from Cardano founder Charles Hoskinson, who noted that the matter was serious enough to warrant the involvement of federal authorities.
Flawed Test That Unraveled the Network
The situation unfolded at 08:00 UTC, after an improperly structured delegation transaction passed validation on updated node versions but was declined by older ones. Consequently, this divergence immediately created two separate ledger states.
Intersect, the ecosystem organization monitoring the anomaly, observed that a similar issue had emerged on the testnet a day earlier. This finding indicates that the problematic transaction was likely tested before it occurred on the main network.
Although the ledger split created confusion throughout the ecosystem, the network itself continued to operate without interruption. Both chains continued processing blocks, and several identical transactions appeared on each, making the fragmentation harder to untangle.
Service Disruptions Spread Across the Ecosystem
As the split deepened, services built on Cardano began to feel the impact. Major exchanges paused ADA deposits and withdrawals to avoid processing transactions on the wrong chain.
Coinbase applied the longest halt, freezing operations for roughly 14 hours. Other platforms, including Upbit and Kraken, paused activity for short periods while verifying chain integrity.
The instability rippled through the supporting infrastructure. Block explorers displayed conflicting or frozen data, and DeFi protocols struggled with mismatched contract states. These inconsistencies delayed transaction confirmations and caused several failed interactions as users unknowingly operated on different versions of the chain.
Coordinated Response Brings the Network Back Together
In the hours that followed, Cardano’s core entities, IOG, the Cardano Foundation, Intersect, and EMURGO, mobilized a unified emergency response.
Developers released patches within three hours of detecting the flaw. Once deployed, the network progressively converged back to a single chain through Cardano’s usual consensus process, completing its recovery by November 22.
Amid the disruption, ADA, the native token of the Cardano blockchain, fell by about 16% before recovering slightly to around $0.4125.
Developer Claims Accident, Hoskinson Signals Intent
The situation escalated further when an X user known as “Homer J” came forward and admitted to causing the split. The user characterized the incident as an unintended outcome of a personal challenge that went wrong. He formally apologized to the community for what they termed a “careless” testing process.
However, Hoskinson publicly rejected that explanation. He described the act as a “premeditated attack” and said federal investigators, including the FBI, had already been notified.
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
A fact sheet later circulated by Hoskinson and Intersect confirmed that relevant authorities were being informed about the developer’s actions.
Internal Fallout as Developer Resigns
Hoskinson’s remarks and the decision to involve law enforcement created concern within parts of the development team.
Soon after the statements were issued, an IOG employee known as “effectfully” on X announced his resignation. He explained that they had contributed to several simulated attack exercises in the past and now worried that future development mistakes could be interpreted as criminal acts.
He added that many vulnerabilities in the computational layer had emerged from their own research, and they had never expected routine testing or experimentation to carry potential legal risk.
Just submitted my resignation letter.
I've fucked up pen testing in a major way once. I've seen my colleagues do the same. I didn't realize there was a risk of getting raided by the authorities because of that + saying mean things on the Internet.
If the Cardano community wants… https://t.co/HFr5KKs8gF
— effectfully (@effectfully) November 22, 2025
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