CVE-2023-34450

CVE-2023-34450 is a low-severity vulnerability in Cometbft with a CVSS 3.x base score of 3.7. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-401.

Key facts

Description

CometBFT is a Byzantine Fault Tolerant (BFT) middleware that takes a state transition machine and replicates it on many machines. An internal modification made in versions 0.34.28 and 0.37.1 to the way struct `PeerState` is serialized to JSON introduced a deadlock when new function MarshallJSON is called. This function can be called from two places. The first is via logs, setting the `consensus` logging module to "debug" level (should not happen in production), and setting the log output format to JSON. The second is via RPC `dump_consensus_state`. Case 1, which should not be hit in production, will eventually hit the deadlock in most goroutines, effectively halting the node. In case 2, only the data structures related to the first peer will be deadlocked, together with the thread(s) dealing with the RPC request(s). This means that only one of the channels of communication to the node's peers will be blocked. Eventually the peer will timeout and excluded from the list (typically after 2 minutes). The goroutines involved in the deadlock will not be garbage collected, but they will not interfere with the system after the peer is excluded. The theoretical worst case for case 2, is a network with only two validator nodes. In this case, each of the nodes only has one `PeerState` struct. If `dump_consensus_state` is called in either node (or both), the chain will halt until the peer connections time out, after which the nodes will reconnect (with different `PeerState` structs) and the chain will progress again. Then, the same process can be repeated. As the number of nodes in a network increases, and thus, the number of peer struct each node maintains, the possibility of reproducing the perturbation visible with two nodes decreases. Only the first `PeerState` struct will deadlock, and not the others (RPC `dump_consensus_state` accesses them in a for loop, so the deadlock at the first iteration causes the rest of the iterations of that "for" loop to never be reached). This regression was fixed in versions 0.34.29 and 0.37.2. Some workarounds are available. For case 1 (hitting the deadlock via logs), either don't set the log output to "json", leave at "plain", or don't set the consensus logging module to "debug", leave it at "info" or higher. For case 2 (hitting the deadlock via RPC `dump_consensus_state`), do not expose `dump_consensus_state` RPC endpoint to the public internet (e.g., via rules in one's nginx setup).

Frequently asked questions

What is CVE-2023-34450?
CometBFT is a Byzantine Fault Tolerant (BFT) middleware that takes a state transition machine and replicates it on many machines. An internal modification made in versions 0.34.28 and 0.37.1 to the way struct `PeerState` is serialized to JSON introduced a deadlock when new function MarshallJSON is called. This function can be called from two places. The first is via logs, setting the `consensus` logging module to "debug" level (should not happen in production), and setting the log output format to JSON. The second is via RPC `dump_consensus_state`. Case 1, which should not be hit in production, will eventually hit the deadlock in most goroutines, effectively halting the node. In case 2, only the data structures related to the first peer will be deadlocked, together with the thread(s) dealing with the RPC request(s). This means that only one of the channels of communication to the node's peers will be blocked. Eventually the peer will timeout and excluded from the list (typically after 2 minutes). The goroutines involved in the deadlock will not be garbage collected, but they will not interfere with the system after the peer is excluded. The theoretical worst case for case 2, is a network with only two validator nodes. In this case, each of the nodes only has one `PeerState` struct. If `dump_consensus_state` is called in either node (or both), the chain will halt until the peer connections time out, after which the nodes will reconnect (with different `PeerState` structs) and the chain will progress again. Then, the same process can be repeated. As the number of nodes in a network increases, and thus, the number of peer struct each node maintains, the possibility of reproducing the perturbation visible with two nodes decreases. Only the first `PeerState` struct will deadlock, and not the others (RPC `dump_consensus_state` accesses them in a for loop, so the deadlock at the first iteration causes the rest of the iterations of that "for" loop to never be reached). This regression was fixed in versions 0.34.29 and 0.37.2. Some workarounds are available. For case 1 (hitting the deadlock via logs), either don't set the log output to "json", leave at "plain", or don't set the consensus logging module to "debug", leave it at "info" or higher. For case 2 (hitting the deadlock via RPC `dump_consensus_state`), do not expose `dump_consensus_state` RPC endpoint to the public internet (e.g., via rules in one's nginx setup).
How severe is CVE-2023-34450?
CVE-2023-34450 has a CVSS 3.x base score of 3.7, rated low severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability low.
Is CVE-2023-34450 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (54th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2023-34450?
CVE-2023-34450 affects Cometbft. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2023-34450?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2023-34450 published?
CVE-2023-34450 was published on 2023-07-03 and last updated on 2026-06-17.

References

Affected products (1)

More vulnerabilities in Cometbft

All CVEs affecting Cometbft →

Other CWE-401 (Missing Release of Memory after Effective Lifetime) vulnerabilities

Browse all CWE-401 (Missing Release of Memory after Effective Lifetime) vulnerabilities →