Securing Pimlico's Account Abstraction Infrastructure

The Challenge: Building the Foundation for Mainstream Web3 Adoption

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In the evolving landscape of blockchain technology, Pimlico recognized a critical barrier to mass adoption: the complex user experience of managing gas fees and wallets. Their solution — a comprehensive infrastructure for ERC-4337 Account Abstraction — aiming to  revolutionize how users interact with decentralized applications across multiple chains.

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However, with this innovation came significant security challenges:

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• Smart Account Vulnerabilities: Any flaw in the account abstraction layer could compromise user funds across multiple chains
• Gas Sponsorship Risks: Their paymaster infrastructure needed protection against economic attacks and fund draining vectors
• Cross-Chain Complexity: Deployment across Ethereum, Polygon, Optimism, Arbitrum and other EVM chains multiplied the attack surface
• Upgradeability Concerns: The protocol's upgrade mechanisms needed to balance security with adaptability

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Our Process: Specialized Audit for Specialized Infrastructure

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When Pimlico engaged Nethermind Security, we recognized this wasn't a standard protocol review, it required specialized knowledge of ERC-4337 and cross-chain security.

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Over a four-week period, our team:

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1. Deep ERC-4337 Expertise: We deployed auditors with specific experience in Account Abstraction implementations
2. Multi-Chain Analysis: We examined how their contracts would behave across different EVM environments
3. Economic Attack Simulation: We built custom tools to simulate potential economic attacks against their gas sponsorship system
4. Transaction Validation Testing: We tested their bundler contracts against various malicious transaction scenarios
5. Cross-Chain Deployment Analysis: We verified consistent behavior across Ethereum, Polygon, Optimism, Arbitrum and other EVM networks

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Findings That Mattered

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Our comprehensive audit uncovered several critical areas for improvement:

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Transaction Bundler Vulnerabilities

We identified potential replay attack vectors in their bundler implementation that could lead to unintended transaction execution. After detailed analysis, we provided specific remediation steps to ensure transactions could only be executed in their intended context.

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‍Paymaster Protection Gaps

The paymaster contracts had subtle vulnerabilities that could potentially allow malicious actors to drain sponsored gas funds. We discovered that under specific conditions, an attacker could manipulate the gas estimation process to extract approximately 0.05 ETH per exploit. We recommended implementing additional validation checks and rate-limiting mechanisms to prevent exploitation.

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Upgrade Mechanism Risks

While their upgrade pattern was well-designed, we highlighted opportunities to enhance transparency and reduce centralization risks through improved timelock mechanisms and emergency procedures.

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Documentation Improvements

We suggested several documentation enhancements to ensure developers integrating with Pimlico's infrastructure would follow secure implementation patterns.

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The Outcome: Secure Infrastructure for Web3 Adoption

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The Pimlico team responded quickly to our findings, implementing key changes before their mainnet deployment:

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• Strengthened all validation mechanisms in their bundler contracts
• Enhanced their paymaster implementation with additional security checks
• Improved their upgrade mechanisms with more robust timelock controls
• Updated their documentation with comprehensive security best practices

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Results: Measurable Security Impact

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The implementation of our recommendations yielded tangible results:

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• Secured infrastructure now processing over 1M transactions monthly across 6 EVM chains
• Protected gas sponsorship system handling millions in transaction fees
• Fortified system architecture enabling thousands of dApps to implement account abstraction
• Zero security incidents since mainnet deployment

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Why This Work Matters

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This engagement exemplifies how specialized security reviews directly contribute to blockchain adoption:

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1. User Experience & Security: By securing account abstraction infrastructure, we helped enable a more user-friendly Web3 without compromising on security
2. Cross-Chain Safety: Our work ensured consistent security across the multiple chains where Pimlico operates
3. Innovation Protection: We helped protect novel technology that pushes the boundaries of what's possible in Web3

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In an ecosystem where infrastructure security affects countless downstream applications, our partnership with Pimlico helps create a safer environment for the entire blockchain ecosystem.

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Nethermind Security

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