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CVE Record

CVE-2021-38194: An issue was discovered in the ark-r1cs-std crate before 0.3.1 for Rust.

An issue was discovered in the ark-r1cs-std crate before 0.3.1 for Rust. It does not enforce any constraints in the FieldVar::mul_by_inverse method. Thus, a prover can produce a proof that is unsound but is nonetheless verified.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

This vulnerability affects the Rust ark-r1cs-std crate before 0.3.1, used in zero-knowledge proof circuits. A faulty inverse multiplication helper could let a malicious prover create a proof that should be invalid but still verifies. Business impact depends on whether affected cryptographic circuits protect assets, authorization, or integrity decisions.

Executive priority

Prioritize based on where zero-knowledge proof verification protects money movement, access, identity, or compliance claims. For exposed proof-verification services, treat remediation as time-sensitive. For unused or internal-only dependencies, validate presence and schedule normal patching.

Technical view

FieldVar::mul_by_inverse in ark-r1cs-std before 0.3.1 did not enforce constraints. In R1CS terms, the circuit could omit the relationship needed to prove a valid inverse multiplication, making proofs unsound while still passing verification. The sources do not provide CVSS, CWE, or broad affected-product metadata.

Likely exposure

Exposure is most likely in Rust projects that depend on ark-r1cs-std before 0.3.1 and use R1CS circuits involving FieldVar::mul_by_inverse. Systems accepting externally supplied proofs have higher practical concern. The source bundle does not identify packaged products or services using the vulnerable crate.

Exploitation context

CISA KEV is false, and the provided sources do not claim active exploitation. Practical abuse would require a system that relies on affected ark-r1cs-std circuit logic and accepts proofs whose soundness depends on this method. No public exploit details are included in the source bundle.

Researcher notes

The core issue is soundness failure, not memory corruption or service disruption. Evidence is strong for the crate-level flaw and fixed version boundary, but incomplete for severity scoring, affected downstream products, and exploitation in the wild. Avoid assuming impact without reviewing actual circuit usage.

Mitigation direction

  • Upgrade ark-r1cs-std to version 0.3.1 or later.
  • Regenerate lockfiles and rebuild dependent Rust proof components.
  • Review circuits that use FieldVar::mul_by_inverse for business-critical assertions.
  • Check RustSec and upstream project guidance for any additional recommendations.

Validation and detection

  • Inspect Cargo.lock and SBOMs for ark-r1cs-std versions before 0.3.1.
  • Search circuit code for FieldVar::mul_by_inverse usage.
  • Run proof verification regression tests covering invalid inverse relationships.
  • Confirm production services run rebuilt artifacts with the updated dependency.
Prepared
Confidence
medium
Sources
4

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

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
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.

0CVSS vectors
0Timeline events
0ADP providers
3Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

No CWE listed

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