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CVE Record

CVE-2021-38196: An issue was discovered in the better-macro crate through 2021-07-22 for Rust.

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.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

This CVE flags the Rust crate better-macro as intentionally demonstrating arbitrary code execution through Rust procedural macros. The bundle says it has no legitimate purpose. Business risk is limited to environments that depend on or build this crate, but any confirmed use should be treated as a supply-chain concern.

Executive priority

Prioritize investigation if the organization builds Rust software. Confirm whether better-macro exists in dependency inventories, then remove or block it if found. No active exploitation evidence is provided, but the crate’s stated purpose makes confirmed usage unacceptable.

Technical view

The reported issue affects the better-macro crate through 2021-07-22. The source description states the crate demonstrates remote arbitrary code execution via proc-macros. No CVSS, CWE, patched version, or product CPE is provided in the bundle, and the affected metadata is effectively unspecified.

Likely exposure

Exposure is most likely in Rust projects, CI systems, or developer workstations that include better-macro directly or through dependency resolution. The provided affected-product data is n/a, so scope cannot be inferred beyond the named crate.

Exploitation context

The bundle does not show CISA KEV listing or cited evidence of active exploitation. Risk comes from compiling or otherwise trusting a crate described as having no legitimate purpose and demonstrating code execution behavior.

Researcher notes

Evidence is sparse but direct: the CVE and RustSec advisory identify better-macro as demonstrating arbitrary code execution via proc-macros and lacking legitimate purpose. No exploit status, fixed release, CVSS, CWE, or affected CPE data is provided.

Mitigation direction

  • Check RustSec advisory guidance before making remediation decisions.
  • Remove or avoid the better-macro crate where present.
  • Audit Rust dependency manifests and lockfiles for better-macro.
  • Review CI build environments that compile affected Rust projects.
  • Apply dependency allowlisting for Rust crates where practical.

Validation and detection

  • Inspect Cargo.toml and Cargo.lock for better-macro.
  • Check dependency inventory for transitive inclusion of better-macro.
  • Review RustSec scan results for RUSTSEC-2021-0077.
  • Confirm CI jobs are not building projects using the crate.
  • Document any confirmed use and owner response.
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

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

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description · low confidence lookup

Execution behavior lookup

The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.

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cve · low confidence lookup

CVE-2021-38196 mapping review

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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

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