Ethereum’s Berlin Upgrade Went Live, Then OpenEthereum Nodes Stalled

Ethereum activated its Berlin mainnet upgrade at block 12,244,000 on April 15, 2021. The block was recorded at 10:07:03 UTC, bringing four Ethereum Improvement Proposals into the network’s operating rules. Within roughly an hour, however, OpenEthereum nodes began stalling at block 12,244,294, interrupting several prominent services that relied on that particular client.

The combination mattered because it demonstrated both sides of a decentralized protocol upgrade. Ethereum’s participating miners and nodes collectively adopted new rules without a central switch being thrown, and the main chain continued producing blocks. Yet a defect in one compatible-looking software implementation disrupted companies whose infrastructure lacked an immediately usable alternative.

Four changes activated at one block

Berlin was a mandatory protocol upgrade rather than an optional application release. Node operators needed Berlin-compatible client software to remain on the chain following the new rules. Operators running incompatible versions risked following a pre-upgrade branch that the broader network no longer recognized.

EIP-2565 reduced the gas charged for Ethereum’s modular-exponentiation precompile, an operation used by several cryptographic systems. Its purpose was to align the fee more closely with measured computational work, not to reduce every Ethereum transaction fee.

EIP-2718 introduced a typed transaction envelope. Previously, adding transaction formats required increasingly complicated compatibility rules. The envelope created a standard way to distinguish legacy transactions from new types and provided infrastructure for future formats.

EIP-2929 changed the gas charged when a transaction first accessed certain accounts or storage locations. It distinguished relatively expensive “cold” first access from cheaper subsequent “warm” access. The specification’s stated rationale included making resource-intensive state-access attacks more expensive.

EIP-2930 then introduced type-one transactions containing optional access lists. A sender could identify accounts and storage keys expected to be touched, prepaying specified access costs and reducing some contract-compatibility risks introduced by EIP-2929.

Berlin did not implement Ethereum’s planned proof-of-stake transition or the EIP-1559 fee-market redesign. Those remained separate future developments on April 15.

One client stopped following the chain

The first public OpenEthereum issue preserved logs from version 3.2.1 showing a node unable to synchronize beyond block 12,244,294. That was 294 blocks after Berlin’s activation block, a simple difference between the two recorded heights rather than a measurement of elapsed time or affected network share.

Contemporaneous reports said the problem affected services including Etherscan, Coinbase, Ledger, BitGo and Coin Metrics. Coinbase temporarily disabled ether and ERC-20 withdrawals and warned that incoming transfers would be delayed. Ledger reported that balances and new transactions might not update in its Ledger Live interface. These were service-layer interruptions; they did not establish that Ethereum itself stopped processing blocks or that user assets disappeared.

The OpenEthereum team identified and applied a fix on April 15, according to contemporaneous reporting. The surviving public issue is useful primary evidence of the stalled block and client version, but it is not a complete incident report and does not quantify every affected node, user or transaction.

The episode gave client diversity an immediate institutional dimension. Ethereum supported multiple independently developed implementations, including Geth, OpenEthereum, Besu and Nethermind. That diversity could contain a defect within one implementation, but only if infrastructure operators actually maintained viable alternatives. A multi-client ecosystem offered little operational protection to a service dependent on one failing client.

Market claims remain limited

Ether traded during a broad cryptocurrency rally surrounding Coinbase’s Nasdaq debut on April 14, but the reviewed records do not provide a single authoritative venue, currency pair, sampling method or event window for isolating Berlin’s market effect. No price or return is therefore attributed to the upgrade or client failure.

Later context

On May 18, 2021, Ethereum Foundation developers disclosed that state-access attacks had posed a serious threat before Berlin. Their later benchmarks indicated that Berlin’s repricing substantially reduced the attack’s efficiency. That disclosure clarifies the security motivation for EIP-2929 but was not public knowledge available to readers on April 15.