TECHNOLOGY

Cardano Network Split Triggers Node Upgrades, Restores Consensus

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United States — Cardano engineers and operators restored network consensus after a chain split that began Friday, November 21, 2025, when a malformed delegation transaction exploited a validation mismatch between node versions. Intersect reported the bug traced to a cryptographic library; nodes running newer software accepted the transaction while older nodes rejected it, producing two parallel chains. Operators coordinated upgrades to node v10.5.3 and issued hotfixes, and developers confirmed no user funds were lost. ADA briefly fell over 6–7% and block production slowed during incident. A user later admitted causing the malformed transaction. Based on 6 articles reviewed and supporting research.

Prepared by Jonathan Pierce and reviewed by editorial team.

Timeline of Events

2022: Bug existed in a cryptographic library on Preview testnet.
20 November 2025: Crafted malformed delegation transaction exposed the bug on testnet.
21 November 2025: Malformed transaction hit mainnet, producing a temporary chain split at ~08:00 UTC.
21 November 2025: Operators upgraded nodes to v10.5.3 and applied hotfixes to converge chains.
22 November 2025: User admitted responsibility; Intersect confirmed no user funds lost.