CVE-2021-41138 is a medium-severity (CVSS 5.3) Improper Input Validation vulnerability in pallet-ethereum. No vendor fix is recorded yet; mitigation options are listed below.
Validity check missing in Frontier
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2021-41138 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,386 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
pallet-ethereumReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects crates.io packages — download data is not available via public APIs for these ecosystems.
Description
Impact
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 done again in the subsequent pallet-evm execution logic. However, do note that a chain ID replay attack was possible. In addition, spamming attacks are of main concerns, while they are limited by Substrate block size limits and other factors.
Patches
The issue is patched in commit 146bb48849e5393004be5c88beefe76fdf009aba.
References
Patch PR: https://github.com/paritytech/frontier/pull/495
For more information
If you have any questions or comments about this advisory:
- Open an issue in Frontier repo
Special thanks
Special thanks to @librelois, @nanocryk and the Moonbeam team for reporting and fixing this security vulnerability.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | pallet-ethereum | all versions | No fix |
Affected Products
frontierparityDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for pallet-ethereum, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Remediation status
No patched version of pallet-ethereum has shipped for CVE-2021-41138 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
Frequently Asked Questions
Is CVE-2021-41138 in your dependencies?
Find it across crates.io, including transitive dependencies.