BounceBit Retires Its Layer 1 Chain After $3.1 Million BB Token Exploit

BounceBit, a Bitcoin-focused financial protocol, is permanently shutting down its namesake Layer 1 blockchain after an attacker exploited a protocol flaw to drain 286.5 million BB tokens from nine mainnet accounts, the project said on August 21. The stolen tokens were worth roughly $3.1 million at the time of the incident, but the damage to the token's supply was far more severe: the haul represented 23% of BB's then-circulating supply of 1.24 billion tokens.

The theft unfolded between August 19 and August 20, when an attacker leveraged a vulnerability in the chain's embedded protocol functions to move funds out of nine accounts without their owners' consent. Across 14 transactions spanning approximately four hours and 52 minutes, the attacker siphoned the tokens before BounceBit halted the network at block 20,702,857.

BounceBit said no private keys were leaked, no signatures were forged, and no wallets, hardware devices, or exchange accounts were compromised. Instead, an authorization bug allowed the attacker to designate an unrelated account as a fund source without that account's consent and then pull tokens from it. The team has not named the specific flaw or published a full technical post-mortem.

The description, however, aligns with a critical vulnerability in Evmos, the Cosmos-based framework on which BounceBit Chain was built. Evmos developers publicly disclosed that flaw in July 2024 and fixed it in a subsequent major release. BounceBit's public chain-node repository has not shipped a release since February 2025, eighteen months before the attack, suggesting the chain had not been actively maintained for some time.

Why the chain is being retired

BounceBit said it evaluated possible technical and operational options before deciding to permanently retire the chain. The first reason: Evmos itself has been discontinued by its developers, making it difficult to rework a codebase that no longer receives upstream support. The vulnerability the attacker exploited was inherent to the Evmos stack.

Second, BounceBit's core products and services are already available on BNB Chain, where user activity had increasingly been concentrated. Migrating to BNB Chain gives the project access to a more mature security infrastructure, deeper liquidity, broader application and wallet compatibility, and a substantially larger base of users and developers.

Token reissuance on BNB Chain

BB will now be reissued as a BEP-20 token on BNB Chain. Balances will be set based on a snapshot taken at block 20,697,260, timestamped August 19, 2026 at 21:02:35 UTC, before the first unauthorized transaction. The migration will happen automatically for matching BNB Chain addresses, including staked and unbonding positions, and users will not need to file separate compensation claims. The 286.5 million tokens moved by the attacker will not be included in the new supply.

BounceBit said it has already contacted the nine affected accounts and will restore all balances to their pre-theft state through the snapshot and reissuance process. The project warned users to be alert for phishing scams and fake migration links that may surface during the transition.

Bithumb, one of the exchanges listing BB, suspended deposits and withdrawals for the token on August 20, a day before BounceBit's public disclosure, according to the exchange's notice board.

BounceBit said its CeDeFi strategies, Promo Vaults, Prime, and real-world asset token products were not affected by the exploit and already operate mostly on BNB Chain. The migration represents a hard pivot for the restaking project, which built its identity around a dedicated chain since launching it in May 2024.

The shutdown echoes other recent cases where crypto projects chose to freeze or wind down infrastructure after a security scare rather than patch and continue. The central question now is whether BounceBit can restore user confidence by moving onto another network's rails after its own chain failed a security test.

For token holders and developers, the transition window is delicate. The mechanics of moving assets off a network that is being switched off carry inherent timing and execution risks. BounceBit's own channels will be the authoritative source for migration instructions, and users should treat any other guidance with suspicion as copycat schemes are likely to emerge.

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