What is CVE-2021-42139?

CVE-2021-42139 is a critical-severity vulnerability in Deno Standard Modules, classified under Code Injection. CVSS score: 9.8/10. Published 2021-10-11.

How severe is CVE-2021-42139?

Critical severity. CVSS v3 base score is 9.8 out of 10.

RCE in Deno Standard Modules

CVE-2021-42139

Deno Standard Modules before 0.107.0 allows Code Injection via an untrusted YAML file in certain configurations.

Vulnerability class: RCE (Remote Code Execution)

Published 2021-10-11 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.021 (80.7th percentile), scored 2026-09-30.

Low probability of exploitation in the next 30 days, but still tracked. 81st percentile — 80.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.021 · newest: 0.021 · change: 0.000

Affected products

Deno Standard Modules

Weakness classification (CWE)

CWE-94 — Code Injection

References

github.com/denoland/deno_std/releases/tag/0.107.0 (Third Party Advisory, Release Notes)
github.com/denoland/deno_std/pull/1275 (Exploit, Third Party Advisory)
vuln.ryotak.me/advisories/58 (Third Party Advisory)

Frequently asked questions

What is CVE-2021-42139?: CVE-2021-42139 is a critical-severity vulnerability in Deno Standard Modules, classified under Code Injection. CVSS score: 9.8/10. Published 2021-10-11.
How severe is CVE-2021-42139?: Critical severity. CVSS v3 base score is 9.8 out of 10.