What is CVE-2021-39193?

CVE-2021-39193 is a medium-severity vulnerability in Parity Frontier, classified under Improper Input Validation. CVSS score: 5.3/10. Published 2021-09-03.

How severe is CVE-2021-39193?

Medium severity. CVSS v3 base score is 5.3 out of 10.

Improper input validation in Parity Frontier

CVE-2021-39193

Frontier is Substrate's Ethereum compatibility layer. Prior to commit number 0b962f218f0cdd796dadfe26c3f09e68f7861b26, a bug in `pallet-ethereum` can cause invalid transactions to be included in the Ethereum block state in `pallet-ethereum` due to not validating the input data size. Any invalid transactions included this way have no possibility to alter the internal Ethereum or Substrate state. The transaction will appear to have be included, but is of no effect as it is rejected by the EVM engine. The impact is further limited by Substrate extrinsic size constraints. A patch is available in commit number 0b962f218f0cdd796dadfe26c3f09e68f7861b26. There are no workarounds aside from applying the patch.

Vulnerability class: Drupalgeddon 2 (CVE-2018-7600)

Published 2021-09-03 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N.

EPSS exploit prediction

EPSS: 0.012 (66.7th percentile), scored 2026-09-29.

Low probability of exploitation in the next 30 days, but still tracked. 67th percentile — 66.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.012 · newest: 0.012 · change: 0.000

Affected products

Parity Frontier
Paritytech Frontier — versions < 0b962f218f0cdd796dadfe26c3f09e68f7861b26

Weakness classification (CWE)

References

github.com/paritytech/frontier/security/advisories/GHSA-hw4v-5x4h-c3xm (Patch, Third Party Advisory)
github.com/paritytech/frontier/pull/465 (Patch, Third Party Advisory)
github.com/paritytech/frontier/pull/465/commits/8a2b890a2fb477d5fedd0e4335b0062… (Patch, Third Party Advisory)
github.com/paritytech/frontier/commit/0b962f218f0cdd796dadfe26c3f09e68f7861b26 (Patch, Third Party Advisory)

Frequently asked questions

What is CVE-2021-39193?: CVE-2021-39193 is a medium-severity vulnerability in Parity Frontier, classified under Improper Input Validation. CVSS score: 5.3/10. Published 2021-09-03.
How severe is CVE-2021-39193?: Medium severity. CVSS v3 base score is 5.3 out of 10.