CVE-2023-34450

CometBFT PeerState JSON serialization deadlock

Workarounds

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 your nginx setup)

References

• Issue that introduced the deadlock
• Issue reporting the bug via logs

An internal modification 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:

1. Via logs
   • Setting the consensus logging module to "debug" level (should not happen in production), and
   • Setting the log output format to JSON
2. Via RPC dump_consensus_state

Case 1 above, 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 2 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 introduced in versions v0.34.28 and v0.37.1, and will be fixed in v0.34.29 and v0.37.2.

The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap. Typical impact: resource exhaustion leading to denial of service.

CVE-2023-34450 has a CVSS score of 5.3 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.34.29, 0.37.2); upgrading removes the vulnerable code path.

Kodem intelligence

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The PR containing the fix is here, and the corresponding issue is here

1. What is CVE-2023-34450? CVE-2023-34450 is a medium-severity allocation of resources without limits or throttling vulnerability in github.com/cometbft/cometbft (go), affecting versions = 0.34.28. It is fixed in 0.34.29, 0.37.2. The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap.
2. How severe is CVE-2023-34450? CVE-2023-34450 has a CVSS score of 5.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of github.com/cometbft/cometbft are affected by CVE-2023-34450? github.com/cometbft/cometbft (go) versions = 0.34.28 is affected.
4. Is there a fix for CVE-2023-34450? Yes. CVE-2023-34450 is fixed in 0.34.29, 0.37.2. Upgrade to this version or later.
5. Is CVE-2023-34450 exploitable, and should I be worried? Whether CVE-2023-34450 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2023-34450 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2023-34450?
   • Upgrade github.com/cometbft/cometbft to 0.34.29 or later
   • Upgrade github.com/cometbft/cometbft to 0.37.2 or later

Other vulnerabilities in github.com/cometbft/cometbft