# CometBFT denial of service via invalid ValidatorIndex in Vote Extensions

Source: https://junglewise.ai/threats/cometbft-denial-of-service-via-invalid-validatorindex-in-vote-1383acab  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2024-11-06. Updated: 2026-06-08  
License: CC BY 4.0 with a link back

Severity: high · CVSS 8.3 · Published 2024-11-06

CometBFT is a software platform used to build and maintain blockchain networks. A vulnerability exists where a malicious participant in the network can send a specially crafted message that causes other nodes to crash (panic). This can lead to a service outage or disruption of the blockchain's consensus process, though it only affects networks that have specifically enabled the 'vote extensions' feature.

Technologies: [github.com/cometbft/cometbft (Go)](https://junglewise.ai/threats/technologies/github-com-cometbft-cometbft). Vendors: [Go](https://junglewise.ai/threats/vendors/go).

## Quick answers

**Is This vulnerability exploited in the wild?** No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.

**How severe is This vulnerability?** High severity, with a CVSS score of 8.3, published 6 November 2024.

**Which products and versions are affected?** CometBFT >= 0.38.0, < 0.38.15; github.com/cometbft/cometbft (Go) >= 0.38.0, < 0.38.15.

**Is there a fix for This vulnerability?** A patch was published on 2024-10-30: Core team completes patch Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is This vulnerability attacked?** It is attacked over the network, in a software library.

**Am I affected?** Check whether you run CometBFT or github.com/cometbft/cometbft (Go) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A vulnerability in CometBFT's consensus engine allows for a remote denial-of-service (panic). The root cause is an improper validation of the 'ValidatorIndex' field in 'Vote' messages of type 'Precommit' when vote extensions are enabled. Specifically, logic introduced in version 0.38.x to handle vote extensions processes the message before the standard validator index verification occurs. An attacker with a modified node can send a message with an out-of-bounds or invalid index, triggering a runtime panic in receiving nodes. This issue is fixed in CometBFT v0.38.15.

## Affected products

- CometBFT CometBFT >= 0.38.0, < 0.38.15

## Timeline

- 2024-10-21: disclosed: Reported to Cosmos Bug Bounty program
- 2024-10-30: patched: Core team completes patch
- 2024-11-06: advisory: Public advisory released

## References

- [https://api.github.com/users/corverroos](https://api.github.com/users/corverroos)
- [https://github.com/corverroos](https://github.com/corverroos)
- [https://api.github.com/users/corverroos/gists%7B/gist_id%7D](https://api.github.com/users/corverroos/gists%7B/gist_id%7D)
- [https://api.github.com/users/corverroos/repos](https://api.github.com/users/corverroos/repos)
- [https://avatars.githubusercontent.com/u/29249923?v=4](https://avatars.githubusercontent.com/u/29249923?v=4)
- [https://api.github.com/users/corverroos/events%7B/privacy%7D](https://api.github.com/users/corverroos/events%7B/privacy%7D)

## Related threats

- [GO-2026-4361 - Inconsistencies between how commit signatures are verified and how block time is derived in…](https://junglewise.ai/threats/go-2026-4361-inconsistencies-between-how-commit-signatures-are-verified-92e2eeac)
- [CometBFT has inconsistencies between how commit signatures are verified and how block time is derived](https://junglewise.ai/threats/cometbft-has-inconsistencies-between-how-commit-signatures-are-verified-17e99f94)
- [GO-2025-4025 - CometBFT's invalid BitArray handling can lead to network halt in github.com/cometbft/cometbft](https://junglewise.ai/threats/go-2025-4025-cometbft-s-invalid-bitarray-handling-can-lead-to-network-6ea1281e)
- [CometBFT's invalid BitArray handling can lead to network halt](https://junglewise.ai/threats/cometbft-s-invalid-bitarray-handling-can-lead-to-network-halt-df96de9f)
- [GO-2025-3443 - CometBFT allows a malicious peer to stall network by disseminating valid-looking block parts in…](https://junglewise.ai/threats/go-2025-3443-cometbft-allows-a-malicious-peer-to-stall-network-by-84bcffee)