GovernorCompatibilityBravo incorrect ABI encoding may lead to unexpected behavior

Impact

The GovernorCompatibilityBravo module may lead to the creation of governance proposals that execute function calls with incorrect arguments due to bad ABI encoding. This happens if the proposal is created using explicit function signatures, e.g. a proposal to invoke the function foo(uint256) is created as propose([target], [0], ["foo(uint256)"], ["0x00..01"]). If the function selector is provided as part of the encoded proposal data the issue is not present, e.g. the same proposal is created as propose([target], [0], ["0x2fbebd3800..01"]), where 2fbebd38 is the function selector.

We’ve assessed the instances of this contract found on chain, and did not find any occurrence of this bug in the past. Proposal creation through Tally or OpenZeppelin Defender is not affected. The core Governor contract on its own is not affected.

Patches

A fix is included in version v4.4.2 of @openzeppelin/contracts and @openzeppelin/contracts-upgradeable.

Workarounds

Do not create proposals using explicit function signatures. Instead, use the propose function without the signatures argument, and create the proposal using the fully ABI-encoded function call including the function selector in the calldatas argument as explained above.

References

https://github.com/OpenZeppelin/openzeppelin-contracts/issues/3099

Credits

This issue was identified and reported by @GeraldHost.

For more information

If you have any questions, comments, or need assistance regarding this advisory, email us at [email protected].

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