"Every time a long-running contract like this is attacked, it sets DeFi adoption back by six to twelve months." This was the perspective shared by Hasu, Strategy Lead at Flashbots and Strategic Advisor to Lido, following the recent hack of Balancer.
On November 3, the veteran DeFi protocol Balancer suffered an unprecedented hack, resulting in losses of up to $116.6 million.
This massive sum was rapidly siphoned off via a cross-chain callback vulnerability in Balancer V2 pool smart contracts. As of November 4, the attacker was actively swapping the stolen assets for ETH via Cow Protocol.
01 Incident Recap: Massive Funds Vanish in an Instant
The Balancer attack sent shockwaves through the crypto world on November 3, with initial losses estimated at around $70 million, and the figure quickly climbing.
At the time of writing, total losses have reached $116.6 million, marking the most severe security incident in Balancer’s history.
On-chain data reveals that the main assets stolen were liquid staking tokens, including WETH, wstETH, osETH, frxETH, rsETH, rETH, and others.
These assets were spread across multiple chains—ETH, Base, Sonic—with Ethereum suffering the greatest blow, accounting for nearly $100 million in losses.
02 Vulnerability Analysis: A Catastrophe Triggered by a Simple Mistake
Security researchers quickly pinpointed the root cause. According to Defimon Alerts and Decurity, the issue lay in the access control checks of the manageUserBalance function in the Balancer V2 protocol.
When verifying withdrawal permissions, the system should have checked whether the caller was the actual account owner. Instead, the code erroneously validated whether msg.sender (the actual caller) matched the user-supplied op.sender parameter.
Since op.sender is a user-controlled input, attackers could easily spoof their identity and bypass permission checks.
The fact that such a basic access control error appeared in a protocol running for five years left security experts stunned.
03 Historical Perspective: Six Security Incidents in Six Years
If the headline "Balancer Hacked" sounds familiar, you’re not alone. This is actually Balancer’s sixth major security incident in five years.
A look back at Balancer’s security history paints a sobering picture:
- June 2020: Deflationary token vulnerability, ~$520,000 lost
- March 2023: Indirect losses from the Euler incident, ~$11.9 million lost
- August 2023: V2 pool precision bug, ~$2.1 million lost
- September 2023: DNS hijacking attack, ~$240,000 lost
- June 2024: Forked project Velocore hacked, ~$6.8 million lost
Repeated security breaches have exposed the fragile defenses not just of Balancer, but of the broader DeFi ecosystem.
04 Market Impact: Collapsing Confidence and Price Plunge
The market reacted swiftly and sharply. According to CoinMarketCap, the BAL (Balancer) token dropped 7.13% on November 3, closing at $0.92.
BAL’s current market cap stands at around $62.2 million, down approximately $4.78 million from the previous day. Gate platform data shows BAL’s price has been under sustained pressure for some time.
Confidence in Balancer’s security has been severely shaken, with investors actively adjusting their positions and significant sell pressure emerging.
An interesting twist: LookonChain reported that a crypto whale, dormant for three years, suddenly awoke after the Balancer exploit, rushing to withdraw $6.5 million in assets from the platform.
05 Industry Ripple Effect: Emergency Measures and Operations Halted
In response to the crisis, several projects integrated with Balancer took urgent action:
- Lido withdrew its unaffected Balancer positions
- Berachain announced a full network pause for an emergency hard fork to patch BEX vulnerabilities linked to Balancer V2
- Berachain founder Smokey The Bera stated that the Ethena team disabled Bera bridging and suspended related market operations
These moves underscore Balancer’s pivotal role in the DeFi ecosystem and highlight how a single protocol vulnerability can trigger systemic risk.
06 The Future of DeFi Security: From Technical Debt to Risk Management
One of Balancer’s innovations—allowing up to eight tokens with custom weights in a single pool—has also become its Achilles’ heel.
Compared to Uniswap’s streamlined design, Balancer’s complexity grows exponentially. Each added token dramatically expands the pool’s state space and attack surface.
Balancer opted for rapid iteration, layering new features atop legacy code from V1 to V2 and Boosted Pools.
This accumulation of "technical debt" has turned the codebase into a precarious stack of blocks.
In 2025, DeFi security faces new challenges. The TEE.Fail attack demonstrated that even hardware-level security can be bypassed with tools costing just $1,000.
Attack vectors have shifted from smart contract bugs to operational vulnerabilities, with 80.5% of losses now stemming from phishing, fake airdrops, and private key leaks—threats originating off-chain.
To combat these risks, innovations like zero-knowledge cryptography and multisig wallets have helped reduce exploit losses by 90% since 2020.
07 Investor Guide: Navigating Risks with Caution
For investors, this incident is a stark reminder. Navigating the DeFi landscape requires vigilance:
- Withdraw from affected pools: Immediately remove funds from Balancer V2 pools to prevent further losses
- Revoke authorizations: Use Revoke, DeBank, or Etherscan to cancel smart contract permissions for Balancer addresses
- Prioritize audited projects: Favor protocols that combine smart contract audits with real-time monitoring and circuit breakers
- Use multisig wallets: Mitigate single-point-of-failure risks, especially for large holdings
Looking Ahead
As of November 4, the latest updates show the Balancer hacker is actively swapping stolen liquid staking tokens for ETH via Cow Protocol. On-chain analysts have observed the attacker converting assets across multiple chains into ETH, USDC, and other major tokens.
Balancer’s official team has offered a 20% white-hat bounty for the return of stolen assets, valid for 48 hours. However, hopes of recovery are fading.
For observers, DeFi remains a novel social experiment; for participants, each exploit is a costly lesson; for the industry, building a robust DeFi ecosystem is the price of maturity.
