Dragonfly is an open source P2P-based file distribution and image acceleration system. Prior to 2.1.0, the processPieceFromSource method does not update the structure’s usedTraffic field, because an uninitialized variable n is used as a guard to the AddTraffic method call, instead of the result.Size variable. A task is processed by a peer. The usedTraffic metadata is not updated during the processing. Rate limiting is incorrectly applied, leading to a denial-of-service condition for the peer. This vulnerability is fixed in 2.1.0.