Delegatecall risk detection

When this applies

• Any delegatecall site
• Proxy implementations (UUPS, Transparent, Beacon, Diamond)
• Multicall / Multicall3 / batch-execute on the contract itself
• Governor's execute() flow
• Library using X for * where X uses delegatecall
• Generic call-forwarder / Safe modules

Detection patterns

delegatecall to user-controlled address (CRITICAL)

function exec(address impl, bytes calldata data) external {
    impl.delegatecall(data);   // ← attacker provides impl, owns storage + can selfdestruct
}

Uninitialized UUPS implementation (CRITICAL)

The implementation contract, if uninitialized, can be initialized by anyone, then UUPS-upgraded to a selfdestruct impl, bricking the implementation. (Famous: Parity multisig.) Always _disableInitializers() in constructor.

Storage slot collision in proxy (CRITICAL)

Proxy uses slot 0 for admin, impl uses slot 0 for owner → impl writes corrupt proxy admin. Use EIP-1967 namespaced slots.

delegatecall + msg.value (MEDIUM-HIGH)

Forwarding msg.value via delegatecall to a function that doesn't expect ether → trapped funds or double-accounting.

Multicall + delegatecall + msg.sender confusion (HIGH)

Multicall via delegatecall preserves msg.sender, so signed-payload-based functions (permit, ERC-2771) can be combined in surprising ways. Audit each function for "what if called via multicall with attacker-controlled previous step?"

Diamond facet self-destruct (HIGH — pre-EIP-6780)

A malicious or buggy facet that calls selfdestruct deletes the diamond. EIP-6780 limits this to same-tx-deploy, but old diamonds remain at risk. See [[selfdestruct-eip6780]].

Library marked internal actually compiled with delegatecall (HIGH)

Solidity compiles "linked" libraries to delegatecall. Linking the wrong library (or address) bricks downstream contracts.

_authorizeUpgrade missing or weak (CRITICAL)

UUPS upgrade gate. If unguarded, anyone can upgrade the proxy.

function _authorizeUpgrade(address) internal override {}   // ← no auth, anyone upgrades

Cross-contract delegatecall to read-only function (LOW)

Used (rarely) for pattern obfuscation; usually a code smell.

Severity rubric

Remediation patterns

• Never delegatecall a non-allowlisted address. Hardcode or maintain a strict allowlist of valid implementations.
• UUPS: _authorizeUpgrade MUST check onlyOwner (or stricter).
• Implementation constructor: _disableInitializers().
• Use EIP-1967 / EIP-7201 namespaced slots for proxy admin / impl.
• Multicall guard: forbid permit/auth-changing functions in batch, or limit to a non-delegatecall variant.
• After upgrading: verify storage layout via forge inspect.

False-positive notes

• Solady LibClone.deployERC1967 and similar canonical proxy libraries are well-tested.
• delegatecall to an immutable implementation address (set in constructor, not changeable) is much lower risk.

Related

• [[initialization]]
• [[storage-layout]]
• [[access-control]]
• [[selfdestruct-eip6780]]