Solana Anchor Account Validation & Reentrancy Checklist: Preventing Web3 Exploits

Understanding Account Validation in Solana Anchor Programs

Unlike EVM smart contracts where contract state is stored directly inside the contract code, Solana Rust programs are completely stateless. All program state (token balances, user profiles, vault states) is stored in external accounts passed into the program instruction via the Context struct.

If an Anchor smart contract fails to validate account ownership, PDA seeds, or program IDs, an attacker can pass malicious accounts into an instruction and drain user vault funds. This guide details essential security validation checks every Web3 security audit checks for.

Essential Anchor Security Validation Rules

• Signer Validation: Always verify that the transaction authority actually signed the transaction (e.g. #[account(signer)]).
• PDA Seed & Bump Constraints: Use explicit seeds and bump verification to prevent fake account injection.
• Reentrancy & CPI Defense: Solana CPI (Cross-Program Invocations) execute synchronously. Always update internal account state before making CPI calls to external token programs (Checks-Effects-Interactions pattern).

Arithmetic Overflow Protection & Custom Error Enum

Always use checked arithmetic operations in Rust (checked_add, checked_sub, checked_mul) or enable Anchor's safe math features to avoid integer underflow/overflow exploits during token transfers.