Malicious peer can make node stuck in blocksync in github.com/cometbft/cometbft

Summary

CometBFT is a distributed, Byzantine fault-tolerant, deterministic state machine replication engine. In the `blocksync` protocol peers send their `base` and `latest` heights when they connect to a new node (`A`), which is syncing to the tip of a network. `base` acts as a lower ground and informs `A` that the peer only has blocks starting from height `base`. `latest` height informs `A` about the latest block in a network. Normally, nodes would only report increasing heights. If `B` fails to provide the latest block, `B` is removed and the `latest` height (target height) is recalculated based on other nodes `latest` heights. The existing code however doesn't check for the case where `B` first reports `latest` height `X` and immediately after height `Y`, where `X > Y`. `A` will be trying to catch up to 2000 indefinitely. This condition requires the introduction of malicious code in the full node first reporting some non-existing `latest` height, then reporting lower `latest` height and nodes which are syncing using `blocksync` protocol. This issue has been patched in versions 1.0.1 and 0.38.17 and all users are advised to upgrade. Operators may attempt to ban malicious peers from the network as a workaround.

Timeline

1. Feb 3, 2025, 9:20 PM UTCCVE published
2. Feb 4, 2025, 7:15 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: partial

3. Feb 4, 2025, 7:16 PM UTCRecord last updated

Affected versions

• cometbft cometbft

  fixed in 0.38.17

• github.com/cometbft/cometbftGo

  fixed in 0.38.17

• github.com/cometbft/cometbftGo

  fixed in 1.0.1

• github.com/cometbft/cometbftGo

  From 1.0.0-alpha.1 · fixed in 1.0.1

References 3