A Starknet smart contract audit is a security review of code deployed to Starknet, carried out against the Cairo VM with STARK proofs execution model and written in Cairo — covering both the bug classes shared across Cairo / STARK systems and the failure modes specific to Starknet.
Starknet contracts are written in Cairo and run under native account abstraction, which means two of the assumptions Solidity developers carry — integer arithmetic and msg.sender being an EOA — are simply not true.
Cairo's felt252 field arithmetic does not overflow the way integers do, and range checks that are implicit in Solidity must be explicit here. Meanwhile every Starknet account is a contract, so signature validation, multicall behaviour and the meaning of the caller address are all contract-defined and can be surprising.
We review felt arithmetic and range assumptions, account abstraction interactions, L1 to L2 message consumption and replay protection, storage addressing, and the class-hash upgrade model — with proofs of concept on a devnet.
Starknet runs on Cairo VM with STARK proofs, so it inherits the bug classes below from every system in that family.
Starknet contracts are written in Cairo. See our Cairo audit methodology.
We fix a commit hash, agree the in-scope contracts and read your architecture docs, then build a threat model: who the actors are, what the trust boundaries are, and which invariants must never break. Nothing is reviewed against assumptions we have not written down.
Line-by-line review by at least two auditors working independently, focused on authorisation, accounting, upgrade paths, external integrations and the gap between what the code does and what the documentation claims it does. Most critical findings come from this phase, not from tooling.
Static analysers appropriate to the language, plus property-based fuzzing and invariant testing to push the system into states no unit test covers. Tooling is used to widen coverage, never to replace the manual pass.
Candidate findings are proven on a forked network with a working proof of concept. We report what an attacker can actually do and what it costs them, not a theoretical severity label.
Every finding gets a severity rating, reproduction steps, the affected code, the impact in concrete terms and a specific remediation. You get a draft for discussion before anything is finalised.
We re-test every remediation against the original proof of concept and check that the fix has not opened a new path. The final report is yours to publish.
Field arithmetic instead of fixed-width integers, native account abstraction changing what the caller is, an explicit L1/L2 message lifecycle, and a class-hash-based upgrade model. Solidity intuitions do not transfer cleanly.
Yes, current Cairo with Starknet Foundry-based testing and property tests. Legacy Cairo 0 is reviewed manually where a migration is in progress.
Yes — both sides. Most messaging bugs are in how the L1 contract and the L2 contract disagree about consumption and replay.
A repository or contract address, a commit hash to freeze the scope, whatever architecture or spec documentation exists, and a point of contact who can answer design questions. If documentation is thin we will write our understanding of the system back to you and ask you to confirm it — that step alone catches design-level bugs.
A single token contract is 24–48 hours. A typical dApp or mid-sized protocol runs one to two weeks. Large DeFi systems, L2s, bridges and ZK circuits are scoped per project after we have seen the code. We will give you a fixed timeline with the quote, not an estimate that moves.
Yes. Fix review is part of the engagement, not an upsell. We re-run the original proof of concept against your patched code and confirm the fix has not introduced a new path.
Send the repository and a commit hash through the contact form, message @bugtester25 on Telegram, or book a 30-minute scoping call. 200+ protocols audited · $4B+ secured · 0 hacks post-audit. Prefer email? info@safeedges.in.