Unauthenticated Nonce Increment in snow

Impact

There was a logic bug where unauthenticated payloads could still cause a nonce increment in snow’s internal state. For an attacker with the ability to inject packets into the channel Noise is talking over, this allows a denial-of-service type attack which could prevent communication as it causes the sending and receiving side to be expecting different nonce values than would arrive.

Note that this only affects those who are using the stateful TransportState, not those using StatelessTransportState.

Patches

This has been patched in version 0.9.5, and all users are recommended to update.

References

There will be a more formal report of this in the near future.