Balancer Reports November 4 Exploit Impacting Stable Pools Across Multiple Blockchains

Balancer Reports November 4 Exploit Impacting Stable Pools Across Multiple Blockchains

Balancer’s official statement confirms multi-network V2 composable stable pool exploit via batchSwap and upscale flaws, leading to CSP v6 suspension and recovery efforts.

ETH
AVAX
OP

Fact Check
The statement is strongly supported by consistent evidence across multiple, high-authority sources. Every key element of the statement is corroborated:1. **Date (November 4):** Several sources, including those from Bitget and RootData, explicitly identify the event as the "November 4 exploit" or "November 4 attack," confirming the date.2. **Entity (Balancer):** All provided sources unanimously confirm that the DeFi protocol Balancer was the subject of the exploit.3. **Action (Reported an exploit):** The sources confirm an exploit occurred and that Balancer subsequently released incident reports and took immediate action, which constitutes "reporting" the event to the public.4. **Impacted Asset (Stable Pools):** Multiple high-relevance sources from Decrypt, Bankless, and The Defiant specify that the exploit was isolated to Balancer's "V2 Composable Stable Pools."5. **Scope (Multiple Blockchains):** Several sources, including Decrypt, Bankless, and RootData, explicitly state the exploit affected pools across "multiple Ethereum-compatible chains" or "numerous blockchains."There are no conflicting reports among the credible sources. While two lower-authority sources contain a clear date error (listing the year as 2025), this appears to be a typo and does not contradict the specific date of November 4, which is consistently mentioned by other, more reliable sources. The overall evidence is coherent, comprehensive, and leaves little room for doubt.
Summary

In an official update, Balancer revealed that a V2 exploit affected Composable Stable Pools across Ethereum, Base, Avalanche, Gnosis, Berachain, Polygon, Sonic, Arbitrum, and Optimism. Vulnerabilities in batchSwap and upscale functions enabled manipulation of pool balances, prompting suspension of CSP v6 and initiation of recovery measures. The losses are still under verification, and Balancer is working to assess the full impact while continuing recovery actions.

Terms & Concepts
  • Composable Stable Pool: A decentralized finance liquidity pool allowing multiple stablecoins to be traded efficiently.
  • batchSwap: A Balancer pool function allowing multiple token swaps in one transaction; vulnerable code enabled exploitation in this case.
  • upscale function: A function in pool math handling balance scaling, which was exploited to manipulate stable pool balances.