MEV-Boost Withdrawal Bug

Chorus One
Chorus One
March 11, 2024
5 min read
March 11, 2024
5 min read

The following article is a summary of a recent ETHResearch contribution by Chorus One Research, which describes a bug we've encountered in mev-boost, the standard software validators used to solicit blocks from sophisticated, specialized entitites called builders on Ethereum. This bug is not specific to Chorus One; it can affect all Ethereum validators running mev-boost.

To read the full paper, please visit:


Chorus One runs a proprietary version of mev-boost, dubbed Adagio, which optimizes for mev capture by optimizing latency.  Our commitment to Adagio obligates us to have an in-depth understanding of mev-boost and Ethereum's PBS setup in general. As such, we decided to dive deeper, and to make our findings available to the Ethereum community.

In practice, mev-boost facilitates an auction, where the winning builder commits to paying a certain amount of ETH for the right to provide the block that the validator proposing the next slot ("proposer") will include. This amount then accrues to an address provided by the validator, referred to as the "fee recipient".

Proposers and builders do not communicate directly, but exchange standardized messages via a third party called a "relay". The relay can determine the amount paid for a block by comparing the balance of the fee recipient at certain fixed times in the auction.

We have observed that in instances where the block in question coincidentally includes reward withdrawals due to the fee recipient, the relay has been unable to separate these withdrawals from the amount paid by the builder. This leads to an inflated value for the auction payment. This inaccuracy can negatively reflect on the Ethereum network under its current economic model (EIP-1559). Specifically, it may decrease the amount of transactions processed and decrease the amount of ETH burned, thus manifesting a small but measurable negative net outcome for the network overall.

For a deep dive, please visit:

About Chorus One

Chorus One is one of the biggest institutional staking providers globally operating infrastructure for 50+ Proof-of-Stake networks, including Ethereum, Cosmos, Solana, Avalanche, and Near, amongst others. Since 2018, we have been at the forefront of the PoS industry and now offer easy enterprise-grade staking solutions, industry-leading research, and also invest in some of the most cutting-edge protocols through Chorus Ventures.

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