Impact

By frontrunning the creation of a proposal, an attacker can become the proposer and gain the ability to cancel it. The attacker can do this repeatedly to try to prevent a proposal from being proposed at all.

This impacts the Governor contract in v4.9.0 only, and the GovernorCompatibilityBravo contract since v4.3.0.

Patches

The problem has been patched in 4.9.1 by introducing opt-in frontrunning protection.

Workarounds

Submit the proposal creation transaction to an endpoint with frontrunning protection.

Credit

Reported by Lior Abadi and Joaquin Pereyra from Coinspect.

References

https://www.coinspect.com/openzeppelin-governor-dos/