CVE-2023-34450 is a low-severity (CVSS 3.7) CWE-401 vulnerability in github.com/cometbft/cometbft. 2 public exploit or proof-of-concept references are indexed, so weaponization risk is real. A fix is available for github.com/cometbft/cometbft — see the affected versions and patch details below.
CometBFT PeerState JSON serialization deadlock
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2023-34450.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
github.com/cometbft/cometbft🐹github.com/cometbft/cometbftReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
Impact
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:
- Via logs
- Setting the
consensuslogging module to "debug" level (should not happen in production), and - Setting the log output format to JSON
- Setting the
- 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.
Patches
The PR containing the fix is here, and the corresponding issue is here
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_stateRPC endpoint to the public internet (e.g., via rules in your nginx setup)
References
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/cometbft/cometbft | ≥ 0.34.28&&< 0.34.29 | 0.34.29go get github.com/cometbft/cometbft@v0.34.29 |
| 🐹Go | github.com/cometbft/cometbft | ≥ 0.37.1&&< 0.37.2 | 0.37.2go get github.com/cometbft/cometbft@v0.37.2 |
Affected Products
cometbftcometbftResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/cometbft/cometbft, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/cometbft/cometbft to 0.34.29 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-34450 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.
Frequently Asked Questions
Is CVE-2023-34450 in your dependencies?
Find it across Go, including transitive dependencies.