Vulnerability Report

Impact

Smart contract applications that make use of the selfdestruct functionality and their end-users.

Classification

The vulnerability has been classified as high with a CVSS score of 8.2. It has the potential to create a denial-of-service to all contracts that can invoke the selfdestruct function to destroy a smart contract.

Users Impacted

Due to the successfully coordinated security vulnerability disclosure, no smart contracts were impacted through the use of this vulnerability. Smart contract states and storage values are not affected by this vulnerability. User funds and balances are safe.

Disclosure

In Ethermint running versions before v0.17.2, the contract selfdestruct invocation permanently removes the corresponding bytecode from the internal database storage. However, due to a bug in the DeleteAccount function, all contracts that used the identical bytecode (i.e shared the same CodeHash) will also stop working once one contract invokes selfdestruct, even though the other contracts did not invoke the selfdestruct OPCODE.

Additional Details

The same contract bytecode can be deployed multiple times to create multiple contract instances. In the internal database, the bytecode is stored as a key-value entry bytecode hash --> bytecode which is shared by those contracts. Unfortunately, when one of the contracts invokes selfdestruct, it will remove the corresponding bytecode hash -> bytecode entry, and thus it disables all the contracts that share the same bytecode.

The attack scenario is as follows:

1. The malicious attacker identifies a vulnerable contract that can invoke selfdestruct
2. The attacker deploys a copy of the contract with identical bytecode
3. Finally, the attacker triggers the selfdestruct operation on their redeployed contract, actively causing a DoS on the original and vulnerable contract. All transactions will fail until a workaround is used (see below).

Patches

Has the problem been patched? What versions should users upgrade to?