CVE-2021-41138: Parity Frontier

Medium severity, CVSS 5.3. EPSS: 1.4% chance of exploitation in the next 30 days.

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 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. The issue is patched in commit `146bb48849e5393004be5c88beefe76fdf009aba`.

Affected products

• Parity Frontier: from 2021-09-30, before 2021-10-13 (fixed in 2021-10-13)

Published 2021-10-13. Last modified 2026-06-17.