Key Takeaways
How much did hackers steal in the Balancer exploit?
Attackers drained over $128 million across six blockchains, with Ethereum accounting for the largest amount, at $99 million.
What caused the vulnerability?
A faulty access control check in Balancer V2’s smart contracts allowed unauthorized internal withdrawals from boosted pools.
November opens with another major blow to crypto markets as Balancer suffered a devastating $128 million exploit across six blockchains on 3 November.
The attack exploited a critical vulnerability in the protocol’s access control system, draining funds and forcing Berachain to take the unprecedented step of halting its entire network.
Source: X
The hack marks one of 2025’s largest DeFi exploits, coming just as traders hoped for better fortune after October failed to deliver the typical “Uptober” rally many expected.
Six chains compromised in hours
On 3 November 2025, the DeFi protocol Balancer [primarily its V2 vaults and boosted pools] suffered a major exploit.
The exploit was due to a faulty access control vulnerability in smart contract checks, allowing unauthorized internal withdrawals. The attack spread across multiple blockchains within hours.
Ethereum bore the brunt with $99 million stolen, including significant amounts of WETH, osETH, and wstETH. Berachain lost $12.86 million, Arbitrum $6.86 million, BASE $3.9 million, Sonic $3.44 million, Optimism $1.58 million, and Polygon $232,000.
Source: PeckShield
The vulnerability didn’t just affect Balancer’s main deployment.
Protocol forks running on various chains inherited the same security flaw, multiplying the attack surface and enabling hackers to drain funds across the entire ecosystem simultaneously.
Berachain takes drastic action
Berachain validators responded with an emergency measure rarely seen in blockchain networks. The team coordinated a purposeful network halt to perform an emergency hard fork addressing the Balancer-related exploits.
“The Berachain validators have coordinated to purposefully halt the Berachain network as the core team performs an emergency hard fork to address Balancer V2 related exploits on the BEX,” the official announcement stated.
Balancer’s TVL crashes
Balancer’s Total Value Locked plummeted from approximately $443 million to $255.82 million, nearly a 50% drop in hours. The DeFi Llama chart shows a sharp decline as users rushed to withdraw funds and avoid further losses.
Source: DefiLlama
The exodus reflects a loss of confidence in the protocol’s security. Even users on unaffected pools fled, unsure whether additional vulnerabilities might exist.
2025’s hack landscape
The Balancer exploit ranks as the third-largest crypto hack of 2025. North Korea’s Lazarus Group reportedly stole $1.5 billion from Bybit in February, marking the largest crypto theft ever.
Hackers drained $223 million from Cetus Protocol in May. The year has seen over $2.17 billion stolen in the first half alone, with Iran’s Nobitex losing $90 million in June to Israeli-linked Predatory Sparrow, and India’s CoinDCX losing $44.2 million in July.
A rough start to November
The timing compounds the damage to market sentiment.
October 2025 failed to deliver the historical “Uptober” gains traders anticipated, leaving many disappointed. The market suffered one of the largest liquidations in history in October, when almost $20 billion was lost.
Now, November opens with one of the year’s largest DeFi hacks, adding pressure to already cautious markets.
The Balancer team confirmed awareness of the exploit and stated that the investigation was ongoing.
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