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CometBFT's invalid BitArray handling can lead to network halt

High severity GitHub Reviewed Published Oct 14, 2025 in cometbft/cometbft • Updated Oct 14, 2025

Package

gomod github.com/cometbft/cometbft (Go)

Affected versions

<= 0.37.15
>= 0.38.0-alpha.1, <= 0.38.18

Patched versions

0.37.16
0.38.19

Description

Name: ASA-2025-003: Invalid BitArray handling can lead to network halt
Criticality: High (Considerable Impact; Possible Likelihood per ACMv1.2)
Affected versions: <= v0.38.18, <= v0.37.15, and main development branches
Affected users: Validators, Full nodes, Users

Description

A bug was discovered in CometBFT's handling of BitArray's that have a mismatch between the BitArray's expected number of Elems for the specified number of Bits. Additional validation was added to prevent processing BitArray's in this invalid state, as well as guards to prevent panics on BitArray methods if one of these invalid states is processed.

Impact

BitArray's are present in a number of messages received from peers. When handling these messages, insufficient validation was applied to prevent processing messages the aforementioned invalid state. In the worst case, nodes will gossip messages to peers in an invalid state before processing them themselves, leading to a network halt (instead of only the node receiving the malicious message crashing).

Patches

The new CometBFT releases v0.38.19 and v0.37.16 fix this issue.

Unreleased code in the main branch is patched as well.

Workarounds

If a node is able to identify a malicious peer sending these payloads, they can ban the ip address using common tools like iptables.

Timeline

  • October 3, 2025, 11:26am EST: Issue reported to Cosmos Labs via an external team (via their Bug Bounty Program).
  • October 3, 2025, 11:59am EST: Issue triaged by core team and core team completes validation of issue.
  • October 6, 2025, 11:14pm EST: Issue reported to the Cosmos Bug Bounty Program (by original white hat reporter).
  • October 9, 2025, 11:15am EST: Pre-notification delivered.
  • October 10, 2025, 11:37am EST: Core team completes patch for the issue.
  • October 14, 2025, 11:00am EST: Patch made available.

This issue was reported by @whoismxuse to the Cosmos Bug Bounty Program on HackerOne on October 6, 2025. If you believe you have found a bug in the Cosmos Stack or would like to contribute to the program by reporting a bug, please see https://hackerone.com/cosmos.

If there are questions about Cosmos security efforts, please reach out to our official communication channel at [email protected].

A Github Security Advisory for this issue is available in the CometBFT repository. For more information about CometBFT, see https://docs.cometbft.com/.

References

@aljo242 aljo242 published to cometbft/cometbft Oct 14, 2025
Published to the GitHub Advisory Database Oct 14, 2025
Reviewed Oct 14, 2025
Last updated Oct 14, 2025

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Network
Attack Complexity Low
Attack Requirements None
Privileges Required None
User interaction None
Vulnerable System Impact Metrics
Confidentiality None
Integrity None
Availability High
Subsequent System Impact Metrics
Confidentiality None
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

EPSS score

Weaknesses

Improper Handling of Syntactically Invalid Structure

The product does not handle or incorrectly handles input that is not syntactically well-formed with respect to the associated specification. Learn more on MITRE.

CVE ID

No known CVE

GHSA ID

GHSA-hrhf-2vcr-ghch

Source code

Credits

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