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high Bridge / Cross-Chain SWC-121 CWE-294

Bridge Message Replay (No Processed-Nonce Map)

SAFE-0245 Bridge / Cross-Chain Checked automatically by the scanner
1

What goes wrong

An inbound cross-chain message is executed without recording and checking a per-message unique id/nonce. The same proof/message can be submitted repeatedly to mint or release funds multiple times.

2

The vulnerable pattern

proof of concept — how it is exploited
// receiveMessage(proof) mints 100 to user, no processed-map.
// attacker resubmits the identical proof N times -> mints 100*N.
3

How to fix it

the pattern that is safe
require(!processed[msgId], "replayed");
processed[msgId] = true;
_release(to, amount);
◆
Track and reject already-processed message ids.
4

Where this has happened

Largest recorded losses in the same failure class — related, not the same bug:

$586M · 2022 BNB Chain Token Hub Input validation · 2022 $326M · 2022 Wormhole Input validation · 2022 $197M · 2023 Euler Finance Input validation · 2023 $190M · 2022 Nomad Bridge Input validation · 2022
5

Related vulnerabilities in Bridge / Cross-Chain

SAFE-0063Bridge Message Forgery / Insufficient Proof Verification critical · Bridge / Cross-Chain SAFE-0064Cross-Domain Authentication Failure critical · Bridge / Cross-Chain SAFE-0246Cross-Chain Source / Sender Not Verified critical · Bridge / Cross-Chain SAFE-0247chainId Not Bound in Cross-Chain Payload medium · Bridge / Cross-Chain SAFE-0248Cross-Chain Message Ordering Not Enforced medium · Bridge / Cross-Chain
← PreviousBatch Operation Depends on Block Gas Limit
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