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CometBFT allows a malicious peer to make node stuck in blocksync

Moderate severity GitHub Reviewed Published Feb 3, 2025 in cometbft/cometbft • Updated Mar 9, 2026

Package

gomod github.com/cometbft/cometbft (Go)

Affected versions

>= 1.0.0-alpha.1, < 1.0.1
< 0.38.17

Patched versions

1.0.1
0.38.17

Description

Name: ASA-2025-001: Malicious peer can disrupt node's ability to sync via blocksync
Component: CometBFT
[OUTDATED] Criticality: Medium (Considerable Impact; Possible Likelihood per ACMv1.2)
Update of Criticality on 2026-03-06: We've made a mistake and over-rated the criticality of this bug in our initial triage. We have calibrated our vulnerability rating internally and updated the criticality of this bug to be Informational (Negligible Impact, Possible Likelihood)
Affected versions: <= v0.38.16, v1.0.0
Affected users: Validators, Full nodes

Impact

A malicious peer may be able to interfere with a node's ability to sync blocks with peers via the blocksync mechanism.

In the blocksync protocol peers send their base and latest heights when they connect to a new node (A), which is syncing to the tip of a network. base acts as a lower ground and informs A that the peer only has blocks starting from height base. latest height informs A about the latest block in a network. Normally, nodes would only report increasing heights:

B: {base: 100, latest: 1000}
B: {base: 100, latest: 1001}
B: {base: 100, latest: 1002}
...

If B fails to provide the latest block, B is removed and the latest height (target height) is recalculated based on other nodes latest heights.

The existing code hovewer doesn't check for the case where B first reports latest height X and immediately after height Y, where X > Y. For example:

B: {base: 100, latest: 2000}
B: {base: 100, latest: 1001}
B: {base: 100, latest: 1002}
...

A will be trying to catch up to 2000 indefinitely. Even if B disconnects, the latest height (target height) won't be recalculated because A "doesn't know where 2000" came from per see.

Impact Qualification

This condition requires the introduction of malicious code in the full node first reporting a non-existing latest height, then reporting lower latest height and nodes which are syncing using blocksync protocol.

Patches

The new CometBFT releases v1.0.1 and v0.38.17 fix this issue.

Unreleased code in the main is patched as well.

Workarounds

When the operator notices blocksync is stuck, they can identify the peer from which that message with "invalid" height was received. This may require increasing the logging level of the blocksync module. This peer can then be subsequently banned at the p2p layer as a temporary mitigation.

References

If you have questions about Interchain security efforts, please reach out to our official communication channel at security@interchain.io. For more information about the Interchain Foundation’s engagement with Amulet, and to sign up for security notification emails, please see https://github.com/interchainio/security.

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

EDIT:

Please notice that this has been updated to be informational severity. This can be avoided by ensuring that one is not connected to a malicious peer during blocksync.

References

@zrbecker zrbecker published to cometbft/cometbft Feb 3, 2025
Published to the GitHub Advisory Database Feb 3, 2025
Reviewed Feb 3, 2025
Published by the National Vulnerability Database Feb 3, 2025
Last updated Mar 9, 2026

Severity

Moderate

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 Low
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:L/SC:N/SI:N/SA:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(38th percentile)

Weaknesses

Improper Check or Handling of Exceptional Conditions

The product does not properly anticipate or handle exceptional conditions that rarely occur during normal operation of the product. Learn more on MITRE.

CVE ID

CVE-2025-24371

GHSA ID

GHSA-22qq-3xwm-r5x4

Source code

Credits

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