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CometBFT has inconsistencies between how commit signatures are verified and how block time is derived

High severity GitHub Reviewed Published Jan 23, 2026 in cometbft/cometbft • Updated Feb 27, 2026

Package

gomod github.com/cometbft/cometbft (Go)

Affected versions

>= 0.38.0-alpha.1, <= 0.38.20
<= 0.37.17

Patched versions

0.38.21
0.37.18

Description

CSA-2026-001: Tachyon

Description

Name: CSA-2026-001: Tachyon

Criticality: Critical (Catastrophic Impact; Possible Likelihood per ACMv1.2)

Affected versions: All versions of CometBFT

Affected users: Validators and protocols relying on block timestamps

Description

A consensus-level vulnerability was discovered in CometBFT's "BFT Time" implementation due to an inconsistency between how commit signatures are verified and how block time is derived.

This breaks a core BFT Time guarantee: "A faulty process cannot arbitrarily increase the Time value."

Impact

Downstream impact on chains affects any module, smart contract, or system that relies on the block timestamp.

Patches

The new CometBFT releases v0.38.21 and v0.37.18 fix this issue. The main unreleased branch is also patched.

Workarounds

There are no effective workarounds for this vulnerability. Upgrading to patched versions is required.

Timeline

  • January 8, 2026, 5:27PM UTC: Issue reported to Cosmos Bug Bounty Program
  • January 9, 2026, 4:55AM UTC: Issue triaged and validated by core team
  • January 12, 2026, 10:25PM UTC: Core team completes patch for the issue
  • January 13, 2026 4:41PM UTC: Pre-notification delivered to ecosystem partners
  • January 23, 2026, 3:00PM UTC: Patch made available

Credits

This issue was reported to the Cosmos Bug Bounty Program on HackerOne. Credit to SEAL 911 and QED Audit for the discovery and help with the patch.

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 you have questions about Cosmos security efforts, please reach out to our official communication channel at security@cosmoslabs.io.

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 Jan 23, 2026
Published to the GitHub Advisory Database Jan 23, 2026
Reviewed Jan 23, 2026
Last updated Feb 27, 2026

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 Low
User interaction None
Vulnerable System Impact Metrics
Confidentiality None
Integrity High
Availability None
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:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N

EPSS score

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

No known CVE

GHSA ID

GHSA-c32p-wcqj-j677

Source code

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