Today’s Ethereum contracts route billions in value, yet incident forensics keep repeating the same refrain: most exploits trace back to a handful of predictable logic mistakes.
A rigorous Solidity audit surfaces those traps before mainnet, but only if the process is thorough and collaborative. The walkthrough below explains how an audit unfolds, the flaws auditors still find most frequently in 2025, how static and dynamic techniques complement each other, and why transparent reporting serves as the bridge between security teams and developers.
Teams that need an end-to-end review can start with Three Sigma’s Solidity audit service.
The Solidity Audit Process Step by Step
- Scoping and Architecture Intake: Auditors map contract roles, proxy patterns, upgrade paths, and external integrations. A 2024 ACM survey revealed that 64% of critical bugs originate from design-level oversights, making it crucial to identify high-risk patterns early;
- Code Freeze and Automated Static Analysis: Tools such as Slither, Mythril, and Semgrep-Solidity scan the repository, flagging deterministic patterns like unchecked delegatecalls or dangerous tx.origin checks. In a large-scale NFT study of 49,940 verified contracts, Slither identified hidden backdoors in 3.8% of the samples;
- Manual Line-by-Line Review: Human engineers inspect business logic, privilege hierarchies, and upgrade storage layouts. They model how contract state flows across modules, catching emergent conditions that scanners miss;
- Dynamic Testing and Fuzzing: Foundry-based fuzzers and invariant suites hammer functions with randomized inputs. Echidna and other generators search for assertion failures and revert mismatches. Adding fuzzing finds roughly 15% more medium-severity issues than static analysis alone;
- Sign-Off and Publication: The final report lists findings, severity, remediation status, and a hash of the audited commit so future changes are obvious.
Common Vulnerabilities Found in Solidity Contracts
| Flaw Category | Why it Matters | Mitigation Patterns |
| Reentrancy on State-Changing External Calls | Still the root cause behind multi-million-dollar drains (DAO 2016; multiple DeFi pools 2023). | Pull over push payments, Checks-Effects-Interactions pattern, or OpenZeppelin ReentrancyGuard. |
| Improper Access Control | Using tx.origin or forgetting role modifiers allows anyone to trigger admin functions; 2024 case studies show that 22% of critical bugs fell into this category. | Strict msg.sender checks, OpenZeppelin AccessControl, multi-sig gated upgrades. |
| Delegatecall Misuse and Proxy Collisions | Delegatecall into untrusted logic or misaligned storage corrupts state or hands control to attackers. | Fixed implementation registries, EIP-1967 layout, UUPS pattern with upgrade authorization. |
| Unchecked Self-destruct Paths | Contracts that allow any caller (or an unrevoked owner) to trigger selfdestruct can brick systems or reroute ether. | Disable destruct functions post-initialization or guard them behind time-lock governance. |
| Timestamp or Block-number Dependence | Miners can nudge timestamps ±15 s; gambling or auction logic that ties payouts to exact time can be gamed. | Add time buffers, rely on blockhash randomness commit-reveal, or use off-chain keepers. |
| Signature Replay and Permit Misuse | Incorrect nonce handling lets attackers reuse signed approvals on other chains or contracts. | EIP-712 domain separators, nonce-increment per successful permit, and chain-ID binding. |
| Gas Griefing and Denial-of-Service via Heavy Loops | Functions that iterate over dynamic arrays can run out of gas, locking user funds or blocking governance proposals. | O(1) writes with mappings, chunked processing, or off-chain snapshotting. |
| Logic Gaps in Pausability and Emergency Controls | Improper ordering of require(!paused) or forgotten pauser role prevents freezes during an exploit. | Use battle-tested Pausable mixins and unit-test pause/unpause paths. |
| Oracle and Price-Manipulation Vectors | Relying on single unsecured oracles allows flash-loan price swings; Ronin Bridge’s 2022 loss originated with oracle trust assumptions. | Multi-source oracles, time-weighted averages, and on-chain sanity bounds. |
Static vs. Dynamic Analysis in Solidity Auditing
Static analysis inspects code without execution.
- Strengths: Speed, full path coverage for deterministic patterns, and CI integration;
- Weaknesses: Higher false positives, limited visibility into runtime values, and no insight into economic behavior.
Dynamic analysis executes contracts on forked chains or in symbolic environments.
- Strengths: Catches runtime-only bugs (reverts, assertion failures), validates gas usage, and uncovers state-dependent vulnerabilities;
- Weaknesses: Path explosion, longer runtimes, and need for solid test oracles.
The most effective Solidity audit uses both: static scanners triage low-hanging fruit, while fuzzers and scenario tests stress live state transitions. A 2024 benchmark showed that hybrid pipelines detect 93% of known security patterns, compared to 74% for static-only and 68% for dynamic-only pipelines.
Reporting and Developer Collaboration
Audits deliver value only when findings are translated into actionable fixes. Best practice reporting includes:
- Clear Severity Ratings: Critical, high, medium, low, and informational, tied to exploitability and impact. EtherAuthority’s 2024 report format, now an industry template, makes fix-priority obvious;
- PoC and Reproduction Steps: Minimal scripts or Foundry tests that trigger the bug, helping developers confirm fixes without guesswork;
- Suggested Remediation: Concrete code snippets or design alternatives, not vague advice;
- Gas and Performance Notes: Optimizations that shave costs often emerge during security review. Auditors annotate trade-offs so teams can decide;
- Version-Controlled Dialogue: Findings tracked in GitHub issues or secure portals, with tags for status (open, in review, fixed, retested). This loop tightens feedback and preserves an audit trail for regulators and future maintainers;
- Re-Audit Sign-Off: After patches, auditors rerun tools and manual tests, then update the report with “fix verified” labels and a hash of the new commit.
Collaborative workflows cut mean-time-to-patch. A recent Webisoft process guide highlights projects that finish remediation in under two weeks when issues are pushed directly into sprint boards, rather than static PDFs.
Closing Thoughts
Solidity’s language safeguards have matured, but logic mistakes remain the primary vector for exploits. An exhaustive Solidity audit combines automated tooling and human insight, surfacing repeat-offender flaws such as reentrancy and access-control gaps, and converting findings into actionable tasks that developers can ship quickly.
Continuous collaboration and periodic re-audits, whenever code or dependencies change, help maintain that security posture.
For projects ready to move from “looks good” to “battle-tested,” engaging a specialist such as Three Sigma’s Solidity audits service ensures every line, modifier, and external call is scrutinized before the chain does it for you.
