One of Ethereum’s leading DeFi protocols, Balancer, which also functions as an established automated market maker (AMM) on the network, suffered a significant vulnerability today (November 3), resulting in losses exceeding $70 million.
On-chain data shows that multiple Balancer liquidity pools were depleted in quick succession, and the stolen tokens were quickly transferred to a newly created wallet controlled by the attacker.
We are aware of a possible exploit affecting Balancer v2 pools.
Our engineering and security teams are investigating with high priority.
We will share verified updates and next steps as soon as we have more information.
– Balancer (@Balancer) November 3, 2025
What we know about the Balancer hack so far
The attack targeted Balancer’s V2 liquidity pools and vaults, exploiting a vulnerability in smart contract interactions. Preliminary analysis by on-chain researchers points to a maliciously implemented contract that manipulated Vault calls during pool initialization.
Improper authorization and callback handling allowed the attacker to bypass security measures. This allowed unauthorized exchanges or balance manipulations between interconnected groups, resulting in the rapid depletion of assets.
The exploiter initiated a series of transactions starting with a key Ethereum mainnet transaction (0xd155207261712c35fa3d472ed1e51bfcd816e616dd4f517fa5959836f5b48569), which funneled assets to a new wallet under their control. The funds were then consolidated, probably for washing through mixers or bridges.
Balancer’s composable design, where groups interact strongly, amplified the flaw. Similar issues have plagued MMAs before, often related to how they handle deflationary tokens or pool rebalancing.
All the forensic details are still emerging, involving auditors like PeckShield and Nansen. There is no evidence that the private key is compromised; This was a pure smart contract exploit.
The rapid execution of transfers suggests that the attacker had deep knowledge of Balancer’s smart contracts, which could exploit a flaw in the way the platform handles swaps or manages fund balances.
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Balancer reacts, community on the limit
As of this writing, Balancer has issued only one update, confirming the hack and assuring the community that an investigation is underway. The DeFi protocols post on X says:
“We are aware of a possible exploit affecting Balancer v2 pools. Our engineering and security teams are investigating with a high priority. We will share verified updates and next steps as soon as we have more information.”
The lack of communication has fueled uncertainty within the DeFi community, as users struggle to understand the extent and cause of the breach.
Blockchain analysts have advised traders to refrain from interacting with Balancer groups until more information is released, warning that additional vulnerabilities may still exist.
Meanwhile, Balancer’s native token, BAL, is down more than 15% in the last 24 hours, due to both unstable market conditions and investor unease with the latest eight-figure exploit.
The worrying thing is that this is not Balancer’s first encounter with hackers. In fact, the platform has suffered three major security incidents in five years, a disturbing record for one of DeFi’s longest-running protocols.
In 2020, attackers exploited Balancer’s handling of deflationary tokens, draining approximately $500,000. Then, in 2023, another vulnerability in its “powered groups” caused losses of $900,000 despite previous security warnings.
The latest $70 million attack dwarfs previous incidents, making it the most serious Balancer exploit to date and one of the biggest DeFi hacks of 2025.
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Balancer Hack Update: More Funds Drained Across Multiple Networks
Update: @Rocker and its forks are under attack, with total losses across multiple chains reaching ~$128.64 million so far. https://t.co/67XGX5RcRR pic.twitter.com/FIwx20ALSz
– PeckShieldAlert (@PeckShieldAlert) November 3, 2025
Several blockchain analysts have posted an update on the Balancer breach in the last hour. So far, the hacker has drained more than $128 million across multiple chains where the Balancer protocol is forked.
Now over $99 million has been stolen from Ethereum, while $12.8 million has been drained from Berachain, $6.8 million from Arbitrum, $3.9 million from Base, $3.4 million from Sonic, $1.58 million from Optimism, and $232 thousand from Polygon.
Hacking of smaller chains represents a significant percentage of the network’s TVL (total value locked). For example, for DefiLlama Data, Sonic has just $150 million in TVL and has sold out for $3.4 million, about 2% of the total value locked on the network.
From an optical point of view, it is worrying that the attack appears to be continuing, with more funds lost even now and no updates from the Balancer team since 10:00 UTC.
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The post Balancer Hack: $70 Million Lost in Record-breaking Ethereum DeFi Breach appeared first on 99Bitcoins.
