CVE-2021-25835
📋 TL;DR
Cosmos Network Ethermint versions up to v0.4.0 have a cross-chain transaction replay vulnerability in the EVM module. This allows attackers to replay valid Ethereum transactions on Ethermint networks, potentially enabling unauthorized fund transfers or contract interactions. Anyone running vulnerable Ethermint nodes is affected.
💻 Affected Systems
- Cosmos Network Ethermint
📦 What is this software?
Ethermint by Chainsafe
⚠️ Risk & Real-World Impact
Worst Case
Attackers could drain funds from accounts by replaying legitimate Ethereum transactions on Ethermint networks, potentially causing significant financial losses.
Likely Case
Unauthorized transaction replay leading to asset theft or unauthorized smart contract interactions on Ethermint-based networks.
If Mitigated
With proper patching, the vulnerability is eliminated by implementing chain-specific transaction signatures.
🎯 Exploit Status
Exploitation requires understanding of both Ethereum and Ethermint transaction structures, but no authentication is needed to submit transactions.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: v0.4.1 and later
Vendor Advisory: https://github.com/cosmos/ethermint/issues/687
Restart Required: Yes
Instructions:
1. Update Ethermint to v0.4.1 or later. 2. Restart all Ethermint nodes. 3. Verify the fix by checking transaction signatures are now chain-specific.
🔧 Temporary Workarounds
Transaction validation middleware
allImplement custom transaction validation to reject transactions with Ethereum chainID signatures
Custom implementation required - no standard commands
🧯 If You Can't Patch
- Monitor for suspicious transaction replays between Ethereum and Ethermint networks
- Implement rate limiting on transaction processing to detect unusual patterns
🔍 How to Verify
Check if Vulnerable:
Check Ethermint version: if <= v0.4.0, system is vulnerableCheck Version:
ethermint versionVerify Fix Applied:
Verify Ethermint version is >= v0.4.1 and test that transactions with Ethereum chainID are rejected📡 Detection & Monitoring
Log Indicators:
- Multiple identical transactions from different chain origins
- Transaction signature validation failures for cross-chain transactions
Network Indicators:
- Unusual transaction patterns matching Ethereum mainnet activity
- Cross-chain transaction attempts
SIEM Query:
transaction.source_chain != current_chain AND transaction.signature_valid = true