CVE-2021-43839Network attack vector

Fee diversion via malformed MsgEthereumTx

Published Dec 21, 2021 · Updated Aug 4, 2024

Integrity flaw in Cronos nodes before 0.6.5 allows remote attackers to divert current-block transaction fees via crafted MsgEthereumTx. The mempool and consensus handlers accepted MsgEthereumTx wrappers without the required extension option, allowing FeeCollector accounting to be bypassed. Unauthenticated network access to a validator node is sufficient; user funds and balances remain safe, while fees for the current block can be diverted.

CVSS severity7.5
High
EPSS probability1.31%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Integrity flaw in Cronos nodes before 0.6.5 allows remote attackers to divert current-block transaction fees via crafted MsgEthereumTx. The mempool and consensus handlers accepted MsgEthereumTx wrappers without the required extension option, allowing FeeCollector accounting to be bypassed. Unauthenticated network access to a validator node is sufficient; user funds and balances remain safe, while fees for the current block can be diverted.

The record

CVE
CVE-2021-43839
Published
Dec 21, 2021
Updated
Aug 4, 2024
Vendor
Cronos Labs
Product
Cronos
Classifications
CWE-670, T1657
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 21, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 0.6.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Cronos Labs · Cronosversion=< 0.6.5

Published CVSS scores

7.5NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-670Always-Incorrect Control Flow Implementation
T1657Financial Theft

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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