CVE-2021-38196

CRITICALNVD 9.89.8—

9.8

An issue was discovered in the better-macro crate through 2021-07-22 for Rust. It intentionally demonstrates that remote attackers can execute arbitrary code via proc-macros, and otherwise has no legitimate purpose.

CVSS v3: 9.8
EG Score: 9.8(medium)
EPSS: 87.5%
KEV: Not listed

Published

August 8, 2021

Last Modified

November 21, 2024

Advisory Details (2)

Auto-updated May 26, 2026

No patch confirmed yet.

generic

RUSTSEC-2021-0077: better-macro: `better-macro` has deliberate RCE to prove a point › RustSec Advisory Database

https://rustsec.org/advisories/RUSTSEC-2021-0077.html

generic

https://raw.githubusercontent.com/rustsec/advisory-db/main/crates/better-macro/RUSTSEC-2021-0077.md

Patch Availability(1)

Vendor / Ecosystem	Fixed in / Patch	Released	Source
rust	better-macro	—	ghsa

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 9× in last 7d / 9× in last 30d)

Every time one of our enrichment pipelines (NVD, MITRE cvelistV5, EPSS, CISA KEV, GHSA, OSV, vendor advisories) ran against this CVE. Most recent first.

2026-05-27 13:39 UTCepss_batch
2026-05-27 13:39 UTCepss_batch
2026-05-27 13:39 UTCepss_batch
2026-05-26 13:42 UTCepss_batch
2026-05-26 12:27 UTCEG score recompute
2026-05-26 12:27 UTCGHSA enrichment
2026-05-26 07:17 UTCepss_batch
2026-05-26 07:17 UTCepss_batch
2026-05-26 07:17 UTCepss_batch

Frequently asked(5)

What is CVE-2021-38196?

CVE-2021-38196 is a critical vulnerability published on August 8, 2021. An issue was discovered in the better-macro crate through 2021-07-22 for Rust. It intentionally demonstrates that remote attackers can execute arbitrary code via proc-macros, and otherwise has no legitimate purpose.

When was CVE-2021-38196 disclosed?

CVE-2021-38196 was first published in the National Vulnerability Database on August 8, 2021, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.

Is CVE-2021-38196 actively exploited?

CVE-2021-38196 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 87.5% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.

What is the CVSS score of CVE-2021-38196?

CVE-2021-38196 has a CVSS v3 base score of 9.8 (NVD).

How do I remediate CVE-2021-38196?

Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-38196, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2021-38196

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