Cardano experienced a brief chain split on Friday due to an old code vulnerability, which may not have been followed up on as it was "unused".

On November 23, Cointelegraph reported that the Cardano network experienced a temporary chain split on Friday due to a “format error” in a delegated transaction. This type of delegated transaction refers to transactions that delegate ADA to a staking pool, which, although valid at the protocol layer, can lead to code glitches that affect network functionality. According to an incident report released by the Cardano ecosystem organization Intersect, this “format error” transaction exploited an old code vulnerability in the underlying software library of the Cardano blockchain, causing nodes to have discrepancies in how they processed the transaction, ultimately leading to the network split. This vulnerability was caused by an ADA staking pool operator named Homer J, who used AI-generated code to facilitate the transaction and has admitted responsibility for the network split. Staking pool operators have been asked to download the latest version of the node software to fix the issue and to reintegrate the split chains into a single complete blockchain. This temporary split has sparked debate within the Cardano community, with some arguing that Homer J's actions helped expose critical vulnerabilities, while others, such as Cardano founder Charles Hoskinson, called it an attack on the Cardano network, prompting an investigation by the FBI. Meanwhile, one user joked, “No one noticed Cardano's network partition because no one is using it.”