Delayed Bitcoin Withdrawals
Incident Report for ZetaChain
Postmortem

Incident Summary

Outbound Bitcoin transactions were delayed by an edge case involving a Cross-Chain Transaction (CCTX) sent from BTC to an EVM contract that was subsequently reverted by the EVM contract. The reverted transaction balance to the BTC network was so small it was rejected by the Bitcoin network.

Impact

Outbound Bitcoin transactions were unable to be processed until a patch was released.

Root Cause

Outbound Bitcoin transactions were blocked by an edge case involving a Cross-Chain Transaction (CCTX) from BTC to an EVM contract that was reverted by the EVM chain. The reverted transaction balance sent to the BTC network was so small it was rejected by the network. These small "dust" transactions are normally avoided automatically by the protocol but in this specific edge case it was not. Failed attempts to send this dust transaction prevented new BTC transactions from being processed until a software update was deployed.

The Bitcoin TSS operates sequentially, meaning if a withdrawal is blocked due to rejected transactions, subsequent withdrawals cannot be processed until the blocked transaction is bypassed.

Resolution

A software update was deployed to automatically skip withdrawals containing dust amounts. Since these withdrawals hold minimal value and would normally be rejected by the Bitcoin network, skipping them will not impact overall processing or cause any loss of funds to users.

Posted Nov 13, 2024 - 23:27 UTC

Resolved
All BTC transactions are being processed normally.
Posted Nov 12, 2024 - 04:32 UTC
Identified
We have identified the issue and are developing a fix.
Posted Nov 11, 2024 - 16:44 UTC
Investigating
Bitcoin withdrawals from ZetaChain to Bitcoin are currently experiencing delays. We are actively investigating the cause to resolve this issue.
Posted Nov 11, 2024 - 11:38 UTC
This incident affected: Mainnet (ZetaChain Mainnet, CCTX - Bitcoin).