Balancer Loses $128M in Exploit That May Have Been Months in the Making

On November 3, 2025, decentralized finance platform Balancer experienced one of the year’s most severe crypto exploits. Losses totaling $128.64 million impacted users across multiple blockchain networks.

The attack targeted Balancer’s V2 Compostable Stable Pools at 7:48 AM UTC. Balancer confirmed the exploit affected its V2 smart-contract architecture on Ethereum mainnet and several layer-2 networks.

The company stated its team is working with leading security researchers to investigate the issue. Balancer clarified that only V2 Compostable Stable Pools were compromised, while V3 and other pool types remained unaffected.

Today, around 7:48 AM UTC, an exploit affected Balancer V2 Composable Stable Pools.

Our team is working with leading security researchers to understand the issue and will share additional findings and a full post-mortem as soon as possible.

Because these pools have been live… pic.twitter.com/LRLNNXogt3

— Balancer (@Balancer) November 3, 2025

Balancer’s Technical Vulnerability Behind the Multi-Million Dollar Breach

GoPlus Security identified a precision rounding error in the Vault’s swap calculations as the exploit’s root cause. Each swap operation rounded down token amounts, creating tiny discrepancies that attackers exploited repeatedly.

1/4 Balancer V2 Attack Analysis

Balancer V2 and its forks suffered a devastating attack across multiple chains, resulting in over $128M in losses. GoPlus detected and alerted users immediately. Here's what happened and how the attacker exploited a critical vulnerability. 🧵 pic.twitter.com/oZpOIKLD9Q

— GoPlus Security 🚦 (@GoPlusSecurity) November 3, 2025

The perpetrators used the batchSwap function to chain multiple swaps together. These compounding rounding losses created significant price distortions within the protocol.

Lookonchain data also revealed attackers transferred 6,587 WETH worth $24.46 million, 6,851 osETH valued at $26.86 million, and 4,260 wstETH worth $19.27 million to a new wallet.

The hackers moved quickly. Within an hour, stolen funds surpassed $110 million. Lookonchain reported the total reached $116.6 million before further escalation.

PeckShield’s investigation confirmed the attack spread across multiple chains. Vaults on Sonic, Polygon, and Base networks were compromised and drained, indicating coordinated cross-chain exploitation.

Pattern of Security Incidents Raises Industry Concerns

This incident marks the second major security breach for Balancer. On September 20, 2023, the platform’s frontend came under attack.

Balancer warned users not to interact with its UI during that incident. PeckShield reported $238,000 worth of crypto assets were stolen in the September 2023 attack.

The balancer frontend is under an attack. The issue is currently under investigation. Please do NOT interact with the balancer UI until further notice!

— Balancer (@Balancer) September 19, 2023

Crypto investigator ZachXBT confirmed the amount and shared the attacker’s wallet address. The perpetrator swapped 15.4 ETH for approximately 2,730 AVAX and transferred funds to Mexc exchange.

Meanwhile, Chainalysis had previously warned that 2025 could become the worst year for crypto thefts. The firm’s mid-year update emphasized the escalating threat landscape.

Stolen fund activity emerged as the dominant concern in 2025. Chainalysis reported that with nearly half the year remaining, theft volumes already exceeded all of 2024.

The firm stated that crypto theft surges represent both immediate threats to ecosystem participants and long-term challenges for industry security infrastructure. Other forms of illicit activity showed mixed year-over-year trends.