Cross-Chain Bridge Exploit via Improper Signature Verification

Overview

A critical vulnerability was identified in a major cross-chain bridge protocol that allowed attackers to forge transaction signatures due to improper signature verification mechanisms, resulting in an $18 million exploit.

Technical Details

The vulnerability stemmed from the bridge's validator node implementation that failed to properly verify the v parameter in ECDSA signatures. This allowed attackers to craft malicious signature objects that would pass verification checks despite not being authentic.

Solidity
1// Vulnerable code example
2function verifySignature(bytes32 messageHash, uint8 v, bytes32 r, bytes32 s, address expectedSigner) internal pure returns (bool) {
3    address signer = ecrecover(messageHash, v, r, s);
4    
5    // Vulnerability: does not check for signature malleability
6    // Missing validation for v parameter (should be 27 or 28)
7    
8    return signer == expectedSigner;
9}

test123

Overview

Technical Details

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