CVE-2021-43839: Cronos is a commercial implementation of a blockchain

Q: How do I fix CVE-2021-43839?

cronos: upgrade to 0.6.5; ethermint: upgrade to 0.7.3; evmos: upgrade to newer than 0.4.2. Exact commands for each OS are on this page.

Q: Is CVE-2021-43839 being exploited?

CVE-2021-43839 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2021-43839 affect?

CVE-2021-43839 affects cronos, ethermint, evmos. Severity is high (CVSS 7.5). Cronos is a commercial implementation of a blockchain. In Cronos nodes running versions before v0.6.5, it is possible to take transaction fees from Cosmos SDK's FeeCollector for the current block by sending a custom crafted MsgEthereumTx. T

Q: How urgent is CVE-2021-43839?

Priority 49/100. High severity; Remotely exploitable, no login, no user action

This month

HIGH 7.5REMOTEUPGRADEUPGRADEUPGRADE

CVE-2021-43839 is a high-severity flaw (CVSS 7.5) affecting cronos, ethermint, evmos. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Cronos is a commercial implementation of a blockchain. In Cronos nodes running versions before v0.6.5, it is possible to take transaction fees from Cosmos SDK's FeeCollector for the current block by sending a custom crafted MsgEthereumTx. This problem has been patched in Cronos v0.6.5. There are no tested workarounds. All validator node operators are recommended to upgrade to Cronos v0.6.5 at their earliest possible convenience.

Why this priority

High severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.4% (top 28%)
CISA exploited list	No
Weakness	CWE-670
Published	2021-12-21
Last modified	2026-06-17

Publisher (CNA): GitHub, Inc. · Vendor: crypto

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-12-21 17:15 UTCPublished CVE record published
2026-06-17 04:11 UTCUpdated Record last modified

crypto cronos UPGRADE

Affected: < 0.6.5

Fixed in: 0.6.5

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy cronos || rpm -q cronos || cronos --version

2. UPGRADE to 0.6.5 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade cronos

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade cronos

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

crypto ethermint UPGRADE

Affected: < 0.7.3 · >= 0.8.0 and <= 0.9.0

Fixed in: 0.7.3

Safe to downgrade to: a release before 0.8.0

1. Check installed version

apt-cache policy ethermint || rpm -q ethermint || ethermint --version

2. UPGRADE to 0.7.3 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade ethermint

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade ethermint

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 0.8.0 (Debian / Ubuntu)

apt-cache madison ethermint sudo apt install ethermint=<VERSION_BEFORE_0.8.0> sudo apt-mark hold ethermint

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list ethermint sudo dnf downgrade ethermint-<VERSION_BEFORE_0.8.0> sudo dnf versionlock add ethermint

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

crypto evmos UPGRADE

Affected: <= 0.4.2

Fixed in: newer than 0.4.2

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy evmos || rpm -q evmos || evmos --version

2. UPGRADE to newer than 0.4.2 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade evmos

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade evmos

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-43839?

cronos: upgrade to 0.6.5; ethermint: upgrade to 0.7.3; evmos: upgrade to newer than 0.4.2. Exact commands for each OS are on this page.

Is CVE-2021-43839 being exploited?

CVE-2021-43839 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-43839 affect?

CVE-2021-43839 affects cronos, ethermint, evmos. Severity is high (CVSS 7.5). Cronos is a commercial implementation of a blockchain. In Cronos nodes running versions before v0.6.5, it is possible to take transaction fees from Cosmos SDK's FeeCollector for the current block by sending a custom crafted MsgEthereumTx. T

How urgent is CVE-2021-43839?

Priority 49/100. High severity; Remotely exploitable, no login, no user action

Related CVEs

CVE-2022-35936 HIGH 8.2 UPGRADE UPGRADE Ethermint is an Ethereum library

References

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