Why Modular Designs Expose New Attack Vectors

A malicious sequencer publishes only block headers to Celestia, withholding transaction data. This creates a fragile state where the L2 appears finalized but users cannot reconstruct or challenge it.\n- Attack Vector: Relies on the disconnect between data availability proofs and execution validity.\n- Impact: Can freeze $1B+ in bridged assets on optimistic rollups until the challenge period expires.

A sovereign rollup (e.g., built with Rollkit) uses Celestia for data but its own nodes for settlement. If >33% of these nodes collude, they can fork the chain's history while the DA layer remains oblivious.\n- Attack Vector: Exploits the separation of consensus from data availability.\n- Impact: Enables double-spends and invalid state transitions, breaking the security model of bridges like LayerZero and Across which assume a single canonical chain.

A shared sequencer network (e.g., Espresso, Astria) becomes dominated by a few entities. They can censor, front-run, and extract maximal MEV across all connected rollups simultaneously.\n- Attack Vector: Centralizes a critical liveness component across multiple execution layers.\n- Impact: Creates cross-rollup MEV opportunities orders of magnitude larger than on a single chain, distorting economic incentives for validators.

A bridge like LayerZero or Axelar attests to a state root on Rollup A. If Rollup A experiences a settlement-layer reorg on its host chain (e.g., Ethereum), the attested state becomes invalid, but the bridge message has already been executed on Rollup B.\n- Attack Vector: The asynchronous timing between execution, settlement finality, and cross-chain messaging.\n- Impact: Results in irreversible, invalid cross-chain transactions, a flaw impossible in monolithic environments.

A data availability layer (Celestia, EigenDA) censors transactions for a specific rollup. Because modular rollups lack inherent liveness, they halt entirely. This failure then cascades to every bridge and liquidity network connected to that rollup.\n- Attack Vector: Liveness dependency on an external, potentially malicious DA committee.\n- Impact: Causes systemic risk collapse, freezing assets across a web of interconnected rollups and DeFi protocols like Uniswap.

In a modular stack where settlement (e.g., Ethereum) is a scarce resource, attackers can spam fraudulent proof submissions from a rollup. Honest provers are forced into a costly auction, making validation economically non-viable.\n- Attack Vector: Economic abstraction of settlement security.\n- Impact: Renders fraud proofs or ZK validity proofs practically useless, allowing invalid state to be finalized.

Every new connection between a modular stack and an external chain (e.g., Ethereum L1, Celestia, Polygon Avail) creates a new trust assumption. The security of the entire stack is now the weakest link in its bridge or light client network.\n- Attack Vector: Bridge exploits, light client equivocation, data withholding.\n- Example: A compromised bridge to a shared DA layer can invalidate state proofs across multiple rollups.

Most rollups use a single, centralized sequencer (e.g., OP Stack, Arbitrum) for speed. This creates a single point of failure for censorship and liveness. In a modular world, a sequencer attack can halt an entire ecosystem of app-chains.\n- The Problem: No forced inclusion; users cannot directly submit to L1.\n- The Solution: Builders must prioritize shared sequencer networks like Astria or Espresso for credible neutrality.

In monolithic chains, security is a function of validator stake. In modular designs, you must secure separate budgets for DA sampling, proof verification, and bridge staking. An attacker can target the cheapest component.\n- Key Metric: Total Cost to Corrupt the weakest economic layer.\n- Builder Mandate: Security budgets must be modeled holistically, not per component. A Celestia data blob is cheap; bribing its proof verification on Ethereum is not.

Sovereign rollups (e.g., on Celestia) forgo Ethereum's settlement security for autonomy. This trades social consensus for technical flexibility. Investors must assess the team's ability to coordinate hard forks and manage validator politics—a non-trivial governance burden.\n- The Trade-off: Escape L1 congestion, but you become your own Supreme Court.\n- Precedent: This is the Bitcoin → Litecoin model, not the Ethereum L2 safety net.

In optimistic rollups, the 7-day challenge period is a known MEV opportunity. With modular DA, new delays emerge: data availability sampling time, proof generation/verification latency. Each delay is a window for cross-layer MEV extraction.\n- New Frontier: MEV between DA layer posting and settlement finality.\n- For Builders: Integrate pre-confirmations or encrypted mempools to mitigate.

Using a cost-effective DA layer like Celestia or EigenDA creates systemic correlation risk. An outage or successful attack on the DA layer could simultaneously disable hundreds of rollups and app-chains, regardless of their individual security.\n- The Problem: Diversification is costly; most chains will flock to the cheapest provider.\n- Due Diligence: Investors must audit the cryptoeconomic security and client diversity of the chosen DA provider as a primary risk factor.