Drainage of FeeCollector's Block Transaction Fees in cronos

Impact

In Cronos nodes running versions before v0.6.5, it is possible to take transaction fees from Cosmos SDK’s FeeCollector for the current block by sending a custom crafted MsgEthereumTx.

User funds and balances are safe.

Patches

This problem has been patched in Cronos v0.6.5 on the mempool level.
The next network upgrade with consensus-breaking changes will patch it on the consensus level.

Workarounds

There are no tested workarounds. All validator node operators are recommended to upgrade to Cronos v0.6.5 at their earliest possible convenience.

Credits

Thank you to @zb3 for reporting this issue on Cronos Immunefi Bug Bounty Program, to @cyril-crypto for reproducing the issue and to @yihuang and @thomas-nguy for patching the issue on the CheckTx (mempool) and the DeliverTx (consensus) levels.

For more information

If you have any questions or comments about this advisory:

• Open a discussion in crypto-org-chain/cronos
• Email us at [email protected]