Balancer Hack: $70M Lost in Record Ethereum DeFi Breach

One of Ethereum’s leading DeFi protocols, Balancer, which also functions as an established automated market maker (AMM) on the network, suffered a significant exploit today (November 3), resulting in losses exceeding $70M.

On-chain data shows that multiple Balancer liquidity pools were drained in rapid succession, with the stolen tokens quickly transferred to a newly created wallet controlled by the attacker.

We’re aware of a potential exploit impacting Balancer v2 pools.

Our engineering and security teams are investigating with high priority.

We’ll 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 vaults and liquidity pools, exploiting a vulnerability in smart contract interactions. Preliminary analysis from on-chain investigators points to a maliciously deployed contract that manipulated Vault calls during pool initialization.

Improper authorization and callback handling allowed the attacker to bypass safeguards. This enabled unauthorized swaps or balance manipulations across interconnected pools, 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. Funds were then consolidated, likely for laundering via mixers or bridges.

Balancer’s composable design, where pools interact heavily, amplified the flaw. Similar issues have plagued AMMs before, often tied to how they handle deflationary tokens or pool rebalancing.

Full forensic details are still emerging, with auditors like PeckShield and Nansen involved. There is no evidence of a private key compromise; this was a pure smart contract exploit.

The swift execution of the transfers suggests the attacker had a deep understanding of Balancer’s smart contracts, potentially exploiting a flaw in how the platform handles swaps or manages pool balances.

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Balancer Reacts, Community on Edge

At the time of writing, Balancer has posted just one update, confirming the hack and assuring the community an investigation is underway. The DeFi protocols post on X reads:

“We’re aware of a potential exploit impacting Balancer v2 pools. Our engineering and security teams are investigating with high priority. We’ll 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 scramble to understand the scope and cause of the breach.

Blockchain analysts have advised traders to refrain from interacting with Balancer pools until further information is released, warning that additional vulnerabilities may still be present.

Meanwhile, Balancer’s native token, BAL, has declined by over 15% in the past 24 hours, due to both shaky market conditions and investor unease with the latest eight-figure exploit.

Worryingly, this is not Balancer’s first encounter with hackers. In fact, the platform has now suffered three major security incidents in five years, an unsettling record for one of DeFi’s longest-running protocols.

In 2020, attackers exploited Balancer’s handling of deflationary tokens, draining roughly $500,000. Then, in 2023, another vulnerability in its “boosted pools” led to $900,000 in losses despite prior security warnings.

The latest $70M attack dwarfs those previous incidents, making it Balancer’s most severe exploit to date and one of the largest DeFi hacks of 2025.

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Update to the Balancer Hack: More Funds Drained Across Multiple Networks

Update: @Balancer and its forks are under attack, with total losses across multiple chains reaching ~$128.64M so far. https://t.co/67XGX5RcRR pic.twitter.com/FIwx20ALSz

— PeckShieldAlert (@PeckShieldAlert) November 3, 2025

Multiple blockchain analysts have released an update on the Balancer breach within the last hour. As of now, over $128 million has been drained by the hacker across multiple chains to which the Balancer protocol is forked.

Over $99M has now been stolen from Ethereum, while $12.8M has been drained from Berachain, $6.8M from Arbitrum, $3.9M from Base, $3.4M from Sonic, $1.58M from Optimism, and $232K from Polygon.

The hack on the smaller chains represents a significant percentage of the network’s TVL (Total Value Locked). For example, per DefiLlama data, Sonic has just $150M in TVL and has been drained for $3.4M, approximately 2% of the total value locked on the network.

It is concerning from an optics point of view that the attack appears to be still ongoing, with more funds being lost even now, and no update from the Balancer team since 10:00 UTC.

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