Key takeaways
- A malformed transaction exploited a deserialization bug, causing a temporary chain split on the Cardano mainnet.
- Engineers released hotfixes and node upgrades to resolve the issue, without compromising user funds.
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The Cardano blockchain is returning to normal after a rare chain fork that temporarily split the network into two copies of its ledger.
According to new a report From Intersect, an organization that supports Cardano’s long-term continuity and development, the incident occurred due to a crafted and malformed authorization transaction on November 20.
The transaction exploited a vulnerability in the crypto library dating back to 2022 on the Preview testnet, allowing the network to split into two distinct chains, including “one with the ‘poisoned’ transaction” and a “healthy” chain without it.
Cardano engineers worked through the night to release a hotfix after an incorrect authorization transaction on the testnet revealed a bug. The next morning, the same type of transaction hit the mainnet, causing the network to split into two parallel chains.
Operators and other stakeholders responded quickly by upgrading the nodes to version 10.5.3, effectively bringing the network back to a single chain.
The team says no user funds were affected. The wallet behind the distorted transaction has been identified, with early forensic evidence suggesting ties to a former Incentivized Testnet participant.
The Federal Bureau of Investigation (FBI) was contacted to investigate the event as a possible cyberattack.
“Cardano is a family, sometimes we fight and sometimes we have bad days and good days. It’s not lost on me how tough 2025 will be for all of us,” He said Cardano founder Charles Hoskinson said in a statement. “The network survived. It didn’t stop.”
Following the Intersect report, User X using the name “Homer J” appeared publicly I confess To provoke the distorted treatment that caused the accident.
He described it as a negligent experiment that inadvertently caused a fork in the Cardano network and sent an apology, saying he felt terrible about the disruption and had no malicious intent.
In response, Hoskinson said the rioter is now trying to back down after realizing the FBI was involved.
Cardano works so fast that we split the guy, patched it, and caught it in a day. He was very active in Fake Fred’s fascination. It was completely personal and now he’s trying to undo it because he knows the FBI is actually involved https://t.co/MNK6d7bEWv
– Charles Hoskinson (IOHK_Charles) November 21, 2025
