TenderMint from version 0.33.0 and before version 0.33.6 allows block proposers to include signatures for the wrong block. This may happen naturally if you start a network, have it run for some time and restart it (**without changing chainID**). A malicious block proposer (even with a minimal amount of stake) can use this vulnerability to completely halt the network. This issue is fixed in Tendermint 0.33.6 which checks all the signatures are for the block with 2/3+ majority before creating a commit.
Affected: Go: github.com/tendermint/tendermint
### Description
**Denial of Service**
Tendermint 0.33.0 and above allow block proposers to include signatures for the wrong block. This may happen naturally if you start a network, have it run for some time and restart it without changing the chainID. (It is a [misconfiguration](https://docs.tendermint.com/master/tendermint-core/using-tendermint.html) to reuse chainIDs.) Correct block proposers will accidentally include signatures for the wrong block if they see these signatures, and then commits won't validate, making all proposed blocks invalid. A malicious validator (even with a minimal amount of stake) can use this vulnerability to completely halt the network.
Tendermint 0.33.6 checks all the signatures are for the block with +2/3 majority before creating a commit.
**False Witness**
Tendermint 0.33.1 and above are no longer fully verifying commit signatures during block execution - they stop after +2/3. This means proposers can propose blocks that contain valid +2/3 signatures and then the rest of the signatures can be whatever they want. They can claim that all the other validators signed just by including a CommitSig with arbitrary signature data. While this doesn't seem to impact safety of Tendermint per se, it means that Commits may contain a lot of invalid data **.
_** This was already true of blocks, since they could include invalid txs filled with garbage, but in that case the application knew that they are invalid and could punish the proposer. But since ap…