Diamond (EIP-2535) detection

When this applies

• Any contract using EIP-2535 Diamond Standard
• Custom multi-facet upgradeable systems
• Frameworks: Nick Mudge's diamond-1, Diamond Industries' SoliState, custom diamond impls

Detection patterns

Function-selector collision (CRITICAL)

Two facets implementing the same 4-byte selector (e.g. function foo() and function bar(uint256) that hash to the same selector). Diamond routes to the last-cut facet, but during a cut, the old version may be reachable.

• Required: precompute selector mapping at deploy + verify uniqueness; rerun at every diamond-cut.

Storage namespace collision (CRITICAL)

Two facets using the same bytes32 STORAGE_POSITION slot prefix.

library LibA { bytes32 constant POS = keccak256("auditsentry.a"); }
library LibB { bytes32 constant POS = keccak256("auditsentry.a"); }   // ← collision

Use unique namespace strings per facet.

Init-vs-upgrade confusion (HIGH)

Diamond init runs once via delegatecall to an Init contract. Re-running init after diamond-cut → can re-initialize values or run dangerous code. See [[initialization]].

diamondCut access control (CRITICAL)

function diamondCut(FacetCut[] calldata cuts, address init, bytes calldata data) external {
    // ← no owner check
}

Anyone can add/remove/replace facets.

Removing facet without removing selectors (HIGH)

Facet contract removed from blockchain (selfdestructed pre-6780, or simply deauthorized), but selectors still point to the old address → reverts.

Replacing critical infrastructure facet (CRITICAL)

A malicious facet replacement can hijack the entire diamond. Centralization risk depends on diamondCut authority.

Facet selfdestruct pre-EIP-6780 (HIGH)

Pre-Cancun: a facet calling selfdestruct deletes itself, breaking the diamond. Post-Cancun (EIP-6780): only delete-in-deploy-tx. Existing facets still risky if deployed before. See [[selfdestruct-eip6780]].

Missing IDiamondLoupe (MEDIUM)

Without Loupe, off-chain consumers can't introspect facets. Soft requirement.

Function visibility per facet (MEDIUM)

Internal functions in a facet aren't callable through the diamond (only externals are routed). Devs sometimes mistake the contracts.

Init function reentrancy (HIGH)

init delegate-call during diamond-cut can reenter. Lock during cut.

Multi-facet shared storage (HIGH)

If multiple facets share a storage struct, modifying struct fields requires coordinated upgrades. Refactoring one facet's view of the struct breaks others.

Severity rubric

Remediation patterns

• Use proven framework (Nick Mudge's diamond-1 or LDC) — don't roll your own.
• Maintain off-chain selector registry; gate diamondCut with a Timelock and a CI check that runs diamondCut --dry-run.
• Storage: per-facet namespaced via keccak256("<unique-app-name>.<facet-name>").
• Init: callable only via LibDiamond.diamondCut, never directly.
• Loupe: always implement for introspection.
• Document the storage struct shared by facets in a separate file.

False-positive notes

• Reading-only Loupe call isn't a finding.
• A diamond with a single facet is fine; the complexity surfaces at >2 facets.

Related

• [[storage-layout]]
• [[delegatecall-risks]]
• [[selfdestruct-eip6780]]
• [[centralization-risk]]