CVE-2021-41138: Frontier is Substrate's Ethereum compatibility layer

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MEDIUM 5.3REMOTEUPGRADE

CVE-2021-41138 is a medium-severity flaw (CVSS 5.3) affecting frontier. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Frontier is Substrate's Ethereum compatibility layer. In the newly introduced signed Frontier-specific extrinsic for `pallet-ethereum`, a large part of transaction validation logic was only called in transaction pool validation, but not in block execution. Malicious validators can take advantage of this to put invalid transactions into a block. The attack is limited in that the signature is always validated, and the majority of the validation is

Why this priority

Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	5.3 (Medium)
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-20
Published	2021-10-13
Last modified	2026-06-17

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

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

Am I affected?

Timeline

2021-10-13 16:15 UTCPublished CVE record published
2026-06-17 04:07 UTCUpdated Record last modified

parity frontier UPGRADE

Affected: >= 2021-09-30 and < 2021-10-13

Fixed in: 2021-10-13

Safe to downgrade to: a release before 2021-09-30

1. Check installed version

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

2. UPGRADE to 2021-10-13 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade frontier

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 2021-09-30 (Debian / Ubuntu)

apt-cache madison frontier sudo apt install frontier=<VERSION_BEFORE_2021-09-30> sudo apt-mark hold frontier

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

dnf --showduplicates list frontier sudo dnf downgrade frontier-<VERSION_BEFORE_2021-09-30> sudo dnf versionlock add frontier

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.

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-2021-41138?

frontier: upgrade to 2021-10-13. Exact commands for each OS are on this page.

Is CVE-2021-41138 being exploited?

CVE-2021-41138 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-2021-41138 affect?

CVE-2021-41138 affects frontier. Severity is medium (CVSS 5.3). Frontier is Substrate's Ethereum compatibility layer. In the newly introduced signed Frontier-specific extrinsic for `pallet-ethereum`, a large part of transaction validation logic was only called in transaction pool validation, but not in

How urgent is CVE-2021-41138?

Priority 42/100. Remotely exploitable, no login, no user action

Related CVEs

CVE-2023-45130 HIGH 7.5 UPGRADE Frontier is Substrate's Ethereum compatibility layer
CVE-2023-28431 HIGH 7.5 UPGRADE Frontier is an Ethereum compatibility layer for Substrate
CVE-2022-39242 MEDIUM 5.3 UPGRADE Frontier is an Ethereum compatibility layer for Substrate
CVE-2022-36008 HIGH 7.1 MITIGATE Frontier is Substrate's Ethereum compatibility layer
CVE-2022-31111 MEDIUM 5.3 MITIGATE Frontier is Substrate's Ethereum compatibility layer

References

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