How severe is CVE-2021-38194?

CVE-2021-38194 has a CVSS score of 9.8/10, rated CRITICAL. Immediate patching is strongly recommended.

Which packages are affected by CVE-2021-38194?

CVE-2021-38194 affects the following packages: ark-r1cs-std (crates.io). Ecosystems affected: crates.io.

How do I fix CVE-2021-38194?

Update ark-r1cs-std to 0.3.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-38194 is resolved across your whole dependency graph.

How do I detect CVE-2021-38194 in my crates.io dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for ark-r1cs-std, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2021-38194 if there is no patch (or I can't update yet)?

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.

Is CVE-2021-38194 actively exploited in the wild?

Yes. There are 1 known exploit references for CVE-2021-38194, including 1 in-the-wild exploitation observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2021-38194?

CVE-2021-38194 has an EPSS (Exploit Prediction Scoring System) score of 1.3%, placing it in the 69th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

When was CVE-2021-38194 published, and has it been updated?

CVE-2021-38194 was published on August 25, 2021 and was last updated on November 8, 2023. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🦀

🦀 crates.io

Not in CISA KEV

CRITICAL severity

CVE-2021-38194 — ark-r1cs-std

CRITICALFix: arkworks-rs/r1cs-std#70

CVE-2021-38194 is a critical-severity (CVSS 9.8) vulnerability in ark-r1cs-std. 1 public exploit reference exists, so weaponization risk is real. A fix is available for ark-r1cs-std — see the affected versions and patch details below.

Calculation error in ark-r1cs-std

Also known asRUSTSEC-2021-0075

Published

Aug 25, 2021

Updated

Nov 8, 2023

Affected

1 pkg

Patched

1 / 1

Exploits

1 known

Exploitation data as of Oct 9, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

1.3%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs69th percentile — riskier than 69% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2021-38194 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

1 pkg affected

🦀ark-r1cs-std

Real-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

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.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🦀crates.io	`ark-r1cs-std`	≥ 0.2.0&&< 0.3.1	0.3.1`cargo update -p ark-r1cs-std --precise 0.3.1`

Affected Products

1 product · 1 configurations

Application

ark-r1cs-stdarcworks

< 0.3.1

range

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

An issue was discovered in the ark-r1cs-std crate before 0.3.1 for Rust.…

rustsec.orgNVDAug 2021

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for ark-r1cs-std, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update ark-r1cs-std to 0.3.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-38194 is resolved across your whole dependency graph.
Workarounds
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

O3 Security · Impact-Aware SCA

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