Vulnerability CVE-2020-5303

Tendermint before versions 0.33.3, 0.32.10, and 0.31.12 has a denial-of-service vulnerability. Tendermint does not limit the number of P2P connection requests. For each p2p connection, it allocates XXX bytes. Even though this memory is garbage collected once the connection is terminated (due to duplicate IP or reaching a maximum number of inbound peers), temporary memory spikes can lead to OOM (Out-Of-Memory) exceptions. Additionally, Tendermint does not reclaim `activeID` of a peer after it's removed in Mempool reactor. This does not happen all the time. It only happens when a connection fails (for any reason) before the Peer is created and added to all reactors. RemovePeer is therefore called before `AddPeer`, which leads to always growing memory (`activeIDs` map). The activeIDs map has a maximum size of 65535 and the node will panic if this map reaches the maximum. An attacker can create a lot of connection attempts (exploiting above denial of service), which ultimately will lead to the node panicking. These issues are patched in Tendermint 0.33.3 and 0.32.10. ### For more information If you have any questions or comments about this advisory: * Open an issue in tendermint/tendermint * Email us at [security@tendermint.com](mailto:security@tendermint.com) More information can be found here. ### Credits - Ethan Buchman (@ebuchman) for writing a test case for Denial of Service 2 and Tess Rinearson (@tessr) for fixing it - Anton Kaliaev (@melekes) for fixing Denial of Service 1