Bitcoin BIP-110 fork risks replay attacks as miner support hits 2.6%

A potential Bitcoin chain split tied to BIP-110 could let attackers replay transactions across both networks, moving real BTC when holders try to sell forked coins.

Bitcoin holders could lose real BTC selling coins from a BIP-110 chain split before separating balances, as both networks accept the same signed transaction.

"In the next couple of days, a new shitcoin will fork off Bitcoin. It is a big security risk for people who just believe they will get an 'airdrop' and want to sell it," Kevin Loaec, CEO of Wizardsardine and a Bitcoin developer, said on X.

A split would create two transaction histories with identical balances at the point of separation. Someone holding 10 BTC before the fork would control 10 coins on each resulting chain. A buyer could copy the transaction used to transfer the forked coins and broadcast it on the main Bitcoin network, moving the same amount of real BTC. The attack would not drain an entire wallet — only the inputs in the signed transaction would move, with fees charged on both chains.

From block 961,632, nodes enforcing BIP-110 will reject blocks that do not signal support through bit 4, with lock-in no later than block 963,648 and data restrictions active at block 965,664, expected around early September. Until wallets, exchanges, and miners clarify which chain they support, holders who cannot verify their coins are separated face the lowest replay risk by leaving balances unmoved.

How a replay attack could move real BTC

The forked coin may carry little value, but if a buyer offers to purchase it at a premium, holders may try to sell. Because BIP-110 does not automatically make transactions valid on one branch and invalid on the other, ordinary transactions may remain valid on both networks until the chains produce coins unique to their respective histories. Users would need to "split" their coins by obtaining and spending outputs that exist on only one branch before transacting safely.

Loaec said large holders may be targeted first because a successful replay involving their wallets would produce a larger return. US holders could also face tax and record-keeping questions if the minority-chain coins acquire a market value. The immediate concern, however, is technical: spending the new asset could unintentionally transfer an equivalent amount of BTC.

Miner support far below activation threshold

BIP-110, formally the Reduced Data Temporary Softfork, seeks to restrict images, text, and other non-payment data stored through Bitcoin transactions for about one year. Miners can activate the proposal early by marking 1,109 of a 2,016-block difficulty period with a support signal, equal to 55% of blocks. The BIP-110 tracker showed support near 2.6% on Friday, making it possible that enforcing nodes reject the chain backed by most Bitcoin mining power.

A second chain would emerge only if miners continue extending the BIP-110 branch. Without enough mining power, that branch could produce blocks slowly or stop advancing entirely, so the split is possible but not guaranteed. Blockstream co-founder Adam Back and Strategy founder Michael Saylor have opposed BIP-110, citing censorship and chain-split concerns, while Bitcoin developer Luke Dashjr has continued supporting it, arguing that non-payment data increases storage costs and moves Bitcoin away from its monetary purpose.

The mandatory signal window is expected to begin this weekend, although timing could shift because Bitcoin blocks do not arrive at exact ten-minute intervals. Holders who cannot verify that their coins have been separated face the lowest replay risk by waiting until wallets, exchanges, and miners clarify which chain they support.

This article is for informational purposes only and does not constitute investment advice.