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CVE Record

CVE-2021-39193: Transaction validity oversight in pallet-ethereum

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.

MediumCVSS 5.3Not KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

Frontier, ParityTech's Ethereum compatibility layer for Substrate, could record invalid Ethereum transactions as included even though they had no effect. Sources say the EVM rejected these transactions and they could not alter Ethereum or Substrate state. The main business concern is integrity of transaction inclusion records, not theft, outage, or state compromise.

Executive priority

Treat as a moderate integrity issue for Frontier-based blockchain infrastructure. Prioritize patching where transaction inclusion records feed user trust, settlement reporting, monitoring, or compliance workflows. It is not described as enabling state takeover, fund movement, or service disruption.

Technical view

CVE-2021-39193 is a CWE-20 input validation flaw in pallet-ethereum before commit 0b962f218f0cdd796dadfe26c3f09e68f7861b26. Input data size was not validated, allowing invalid transactions into the Ethereum block state. The EVM rejected them, preventing state changes. CVSS is 5.3, medium, with network reachability and low complexity.

Likely exposure

Exposure appears limited to Frontier-based Substrate implementations using pallet-ethereum before the fixed commit. Teams operating or depending on such chains should verify whether their runtime includes the vulnerable code. The source bundle does not identify other affected products or downstream distributions.

Exploitation context

The source bundle does not report active exploitation, and CISA KEV status is false. The advisory describes a network-reachable issue requiring no privileges or user interaction, but with low integrity impact and no confidentiality or availability impact.

Researcher notes

The critical boundary is between transaction inclusion in pallet-ethereum block state and actual EVM execution effects. Sources state invalid included transactions are rejected by the EVM and cannot alter internal Ethereum or Substrate state. Further downstream impact depends on how consumers interpret inclusion versus execution success.

Mitigation direction

  • Apply Frontier commit 0b962f218f0cdd796dadfe26c3f09e68f7861b26 or a release containing it.
  • Update any downstream runtime or fork that vendors vulnerable pallet-ethereum code.
  • Redeploy affected nodes after validating the patched runtime or dependency version.
  • Follow ParityTech Frontier advisory guidance; no workaround is listed besides patching.

Validation and detection

  • Inventory Substrate chains, runtimes, or forks using Frontier pallet-ethereum.
  • Compare deployed code or dependency revisions against commit 0b962f218f0cdd796dadfe26c3f09e68f7861b26.
  • Review build manifests and runtime artifacts for the patched pallet-ethereum logic.
  • Check transaction monitoring assumptions where inclusion may be interpreted as successful execution.
Prepared
Confidence
high
Sources
5

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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ATT&CK lookup starting points

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cwe · low confidence lookup

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cve · low confidence lookup

CVE-2021-39193 mapping review

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Vulnerability profileCVE Program record
Severity
Medium
CVSS
5.3 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
0Timeline events
0ADP providers
5Source links

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
5.3CVSS 3.1MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N3.91.4Primary CVE score

Vulnerability scoring details

Base CVSS 3.1 score

5.3Medium
CVSS 3.1 vector shape for CVE-2021-39193Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
paritytechfrontier< 0b962f218f0cdd796dadfe26c3f09e68f7861b26Listed
Weakness

CWE details

CWE-20

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.