The mempool maintains two data structures to keep track of outstanding transactions: a list and a map. These two data structures are supposed to be in sync all the time in the sense that the map tracks the index (if any) of the transaction in the list.
Unfortunately, it is possible to have them out of sync. When this happens, the list may contain several copies of the same transaction. Because the map tracks a single index, it is then no longer possible to remove all the copies of the transaction from the list. This happens even if the duplicated transaction is later committed in a block. The only way to remove the transaction is by restarting the node.
These are the steps to cause the above duplication problem. Everything should happen within one height, that is no FinalizeBlock
or BeginBlock
ABCI calls should happen while these steps are reproduced:
cache_size
in config.toml
One of the copies of tx1 is now stuck in the mempool's data structures. Effectively causing a memory leak, and having that node gossiping that transaction to its peers forever.
The above problem can be repeated on and on until a sizable number of transactions are stuck in the mempool, in order to try to bring down the target node.
This problem is present in releases: v0.37.0
, and v0.37.1
, as well as in v0.34.28
, and all previous releases of the CometBFT repo. It will be fixed in releases v0.34.29
and v0.37.2
.
The PR containing the fix is here.
cache_size
in config.toml
makes it very difficult to effectively attack a full node.{ "nvd_published_at": "2023-07-03T17:15:09Z", "github_reviewed": true, "github_reviewed_at": "2023-07-05T21:34:45Z", "severity": "HIGH", "cwe_ids": [ "CWE-401" ] }