Vulnerability scanning

Vulnerability Scanning

Overview

Find security vulnerabilities in an EVM contract and return a severity-rated finding set. A pattern match is a hypothesis, not a finding. Every candidate must be confirmed reachable and un-neutralized before it is reported.

The Iron Rule: never report an unconfirmed candidate as a confirmed vulnerability. A false positive that triggers a needless rewrite is its own kind of harm; an unconfirmed-but-flagged item must be labeled as such.

When to Use

• Security-auditing Solidity/Vyper/bytecode before deployment or review
• Symptoms: "is this safe?", "audit this", suspected reentrancy, access-control, tx.origin, delegatecall, selfdestruct, unchecked calls
• Producing a severity-rated report for a contract or PR

Do NOT use for: gas optimization (use gas-optimization) or arbitrage/economic analysis (use arbitrage-analysis).

Workflow

Four reasoning steps, in order. You perform them; they are not scripts.

1. Seek — Read the contract and match it against reference/patterns.md. List every candidate with file:line and its SWC id.
2. Innovate — Beyond the library, reason about contract-specific risks (storage-layout collisions in proxies, oracle manipulation, integer edges). Propose a remediation per candidate.
3. Execute — Confirm each candidate per reference/severity-model.md: check reachability and existing guards. Utilize Action-State Differential Verification (taking pre- and post-trigger state snapshots in a local fork like Foundry) to definitively prove exploitability. Corroborate with tools (Slither, Aderyn, Echidna) if available. Assign final severity; drop neutralized candidates.
4. Manage — Emit the report: each confirmed finding with severity, location, SWC id, impact, and remediation. List dropped candidates and why. State explicitly if Slither was unavailable.

Verification

• Use Bug-Context Extraction (BCE) to isolate focused function-level slices before executing complex tests.
• For static analysis, prefer the MCP tool evm_scan_vulnerabilities (schema-validated findings with code snippets; supports severityFilter and detectors for focused scans). Fall back to raw slither <path> or aderyn only when the MCP server is unavailable. Reconcile findings either way.
• To confirm reachability of a candidate on a local fork, prefer evm_trace_call — the structured call tree shows whether the vulnerable frame executes, what it calls, and where it reverts.
• For proxy storage-collision candidates, use evm_inspect_storage_layout on both implementations and diff the slot assignments.
• For dynamic verification, leverage Foundry/Echidna in a Generate-Repair-Execute (GRE) loop to compile and test Proofs of Concept — the MCP tools evm_compile_and_diagnose and evm_run_tests (structured failures with fuzz counterexamples) drive this loop; fall back to raw forge when the MCP server is unavailable.
• When tools/Foundry are absent, explicitly state so, fall back to manual review, and mark findings as manual review, not tool-confirmed. Never present manual review as tool-confirmed.

Quick Reference

Pattern	Signature	Severity	SWC
Reentrancy	.call{value:	Critical	SWC-107
tx.origin auth	tx.origin	High	SWC-115
Unchecked low-level call	.call( / .delegatecall(	Medium	SWC-104
Reachable selfdestruct	selfdestruct(	High	SWC-106
Unsafe delegatecall	.delegatecall(	Critical	SWC-112
Missing access control	state write, no modifier	High	SWC-105
Timestamp dependence	block.timestamp	Low	SWC-116
EIP-7702 Delegation Risk	signed auth tuples / delegatecall	Critical	-
Transient Storage Lock	TSTORE / TLOAD	High	-
Hardcoded Credentials	privateKey = / apiKey =	Critical	-

Full detail: reference/patterns.md and reference/severity-model.md.

Common Mistakes

• Reporting a grep hit without checking reachability. An internal helper behind a guard is not the same risk as a public path.
• Missing that a nonReentrant guard already neutralizes a candidate.
• Calling a finding tool-confirmed when no tool was run.
• Over-rating style issues as High. Match severity to actual impact.

Red Flags — STOP

• "It matches the pattern so it's a finding" → confirm reachability first.
• "I'll mark it Critical to be safe" → severity must match impact.
• "Slither isn't installed but I'll report findings as confirmed" → mark as manual review.