Cross-chain messaging detection

When this applies

• Any application built on LayerZero, CCIP, Hyperlane, Wormhole, Axelar, Polyhedra ZKBridge
• Native L1↔L2 messengers (Optimism, Arbitrum, Base, zkSync, Linea, Scroll)
• Custom bridges / message-passing layers

Detection patterns

_lzReceive accepts any remote (CRITICAL — LayerZero)

function _lzReceive(bytes calldata srcAddr, bytes calldata payload) internal {
    // no allowlist of trusted remote
    _executeMint(payload);   // ← any chain can mint
}

Required: require(trustedRemote[srcChainId] == srcAddr).

CCIP ccipReceive callable directly (CRITICAL)

function ccipReceive(Any2EVMMessage calldata m) external {   // ← public, no router check
    _execute(m.data);
}

Required: require(msg.sender == address(router)).

Hyperlane handle without ISM check (CRITICAL)

Hyperlane's default ISM is permissive. Apps must set their own. If handle is called by mailbox without app-side validation, anyone can spoof messages.

Wormhole VAA double-spend (CRITICAL)

function complete(bytes calldata vaa) external {
    IWormhole.VM memory vm = wormhole.parseAndVerifyVM(vaa);
    _mint(vm.payload.to, vm.payload.amount);   // ← no per-VAA seen check
}

Required: track usedVAAs[vm.hash] = true after first use.

Replay across chains (CRITICAL)

Same payload accepted on multiple destination chains. Include destination chainId in the signed/verified payload.

Default DVN / ISM / config inheritance (HIGH)

Application doesn't set explicit DVN set (LayerZero V2) or ISM (Hyperlane). Default configs are often weak. Look for explicit setSendLibrary, setReceiveLibrary, setEnforcedOptions, setInterchainSecurityModule.

chainId mapping mistakes (HIGH)

LayerZero EIDs ≠ chainIds. CCIP uses chainSelectors. Map wrong → message goes to wrong chain or stuck forever.

Insufficient gas in _lzSend / _options (MEDIUM)

Receiver runs out of gas → message stuck (LayerZero V2 retry semantics).

Force-include on L1↔L2 messengers (HIGH)

Anyone can force-include an L1→L2 transaction. If app assumes only sequencer can trigger certain flows, force-include breaks the assumption.

L2→L1 withdrawal delay assumption (MEDIUM)

Optimism: 7-day challenge. Arbitrum: 7-day. App that assumes funds arrive instantly L2→L1 → invariant broken.

Pause authority not granular (MEDIUM-HIGH)

Single pause for all routes vs per-route → over- or under-blast-radius.

LayerZero V2 compose reentrancy (HIGH)

_lzReceive triggering a compose call back into lzCompose re-enters during the same message. Treat composed messages as reentrant calls.

Trusted remote table update authority (HIGH)

If setTrustedRemote is onlyOwner and owner is an EOA, the bridge can be silently rerouted. See [[centralization-risk]].

Severity rubric

Remediation patterns

• Always validate msg.sender == router/mailbox/endpoint.
• Always validate srcChain and srcAddress against an allowlist.
• Always include destination chainId in the verified payload.
• Mark messages seen by (srcChain, srcAddr, nonce/hash).
• Configure DVN / ISM / executor explicitly per chain.
• Use chainId-aware helpers for L2 block number / time.
• Per-route pause + global emergency pause.
• Trusted-remote updates via timelock + multisig.

False-positive notes

• Canonical OApp / OFT / OFT-Adapter from LayerZero Labs handle most of the above; verify the app didn't override unsafely.
• CCIP RouterClient / ARM are well-tested; the bug surface is in the app's ccipReceive.

Related

• [[crosschain-messaging-specialist]] (subagent)
• [[signature-replay]]
• [[bridge-specialist]] (asset bridges built on top)