The $PORT3 Exploit: How a Missing ecrecover Zero-Check Cost Millions

Port3 Network (PORT3) Security Incident Analysis

Overview

The Port3 Network ($PORT3) has crashed from $0.03720 to ~$0.00644—an 83% drop that decimated liquidity due to a critical oversight in their signature verification logic. A hacker exploited a classic Solidity vulnerability to mint unauthorized tokens. Below are the confirmed on-chain details:

• Targeted Protocol: Port3 Network

• Vulnerable Contract: 0xb4357054c3da8d46ed642383f03139ac7f090343

• Attacker’s Wallet: 0xb13a503da5f368e48577c87b5d5aec73d08f812e

• Attacker’s profit: Minted 1 billion $PORT3 token worths $13.07 million. Swapped 156M PORT3 for roughly 144.53 BNB ($119.48K).

Technical Deep Dive

Looking at the initiated transactions by the attacker,

The attacker calls first registerChain and registerChains. After that, call bridgeIn again. The free mint of PORT3 token was completed by utilizing bridgeIn.

Let’s take a look at how the registerChains function is implemented in the contract of the PORT3 token’s contract:

The verifySignature Flaw The core vulnerability lies inside the signature verification logic. Here is the step-by-step failure:

• The Port3 team had unset/renounced owner‘s address. This means the owner() function returns default the zero address (0x0000...0000).

• The attacker calls registerChain with an invalid (fake) signature.

• Inside verifySignature, the code calls ecrecover. In Solidity, if ecrecover fails to verify a signature, it does not revert; instead, it returns address(0).

• The code then checks if (recovered == authority).

  • recovered is 0x0 (due to the invalid signature).

  • authority is 0x0 (due to renounced ownership).

  • Result: 0x0 == 0x0 evaluates to TRUE.

Because the code failed to explicitly check that recovered != address(0), the contract accepted the fake signature as valid ownership proof. Therefore, anyone can pass this verification, and the attacker can add the token address to _state.tokenImplementations via registerChains, and then bypass detection in bridgeIn to complete _mint operation.

Conclusion

This incident is a textbook example of why developer assumptions are dangerous. The developers assumed ecrecover would only return a valid address or fail. They forgot the edge case: it returns 0 on failure.

Even if you think the owner will never be 0x0, write your code to handle that possibility. Code lives longer than current operational plans.

Auditors must look for functions that return “default values” (like 0, false, or 0x0) instead of reverting, and ensure those default values cannot be exploited.

$PORT3 didn’t die because of a sophisticated cryptographic break. It died because of a missing zero-check. In Web3, a single missing line of code is the difference between security and a $13 million loss.

Stay safe!