AI from Octane Security has revealed a critical bug in the Nethermind Ethereum client, potentially affecting 38% of mainnet validators.
Octane Security's artificial intelligence has uncovered a significant vulnerability within the Nethermind Ethereum client, which could have impacted the operation of 38% of validators on the Ethereum mainnet.
1/ Octane’s AI identified a high-severity liveness bug in the @Nethermind execution client that could have halted local block production for a substantial portion of @ethereum validators. This issue was promptly addressed through the @ethereumfndn bug bounty program, with no known instances of exploitation. pic.twitter.com/ebdUt31WC8
— Octane Security (@octane_security) February 25, 2026
The vulnerability stemmed from inadequate length equality checks when processing transactions that included large binary data arrays (BLOBs) in Nethermind.
This flaw could have allowed attackers to manipulate BLOB objects, resulting in missed slots for legitimate transaction requests.
Discovered during the integration of the Fusaka update, the issue affected both the Ethereum testnet and mainnet.
Fortunately, the bug has been resolved, and a comprehensive review found no evidence of any successful attacks exploiting the vulnerability.
“Automated security tools excel in identifying exceptional cases that are difficult to analyze manually, but can be easily verified once detected [using AI],” noted representatives from Octane Security in a conversation with blockchain co-founder Vitalik Buterin.
The Ethereum Foundation acknowledged the critical nature of the issue, awarding Octane Security a maximum reward of $50,000 through its bug bounty initiative.
Additionally, it is noteworthy that in February, OpenAI partnered with Paradigm to release a benchmark aimed at evaluating AI agents' capabilities in hacking smart contracts.
