Can Formal Verification Prove the Absence of All Security Vulnerabilities?

No, formal verification cannot prove the absence of all security vulnerabilities. It can only prove that the code correctly implements the formal specification.

If the specification itself is flawed (a "mis-specification bug"), or if the vulnerability lies in the underlying compiler, the Ethereum Virtual Machine (EVM), or the external environment (like an oracle), the formal proof will not catch it. It provides certainty for the code's logic against its stated goals, but not for the entire deployment ecosystem.