CVE-2021-39199

CRITICALNVD 10.010.0—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 10.0 under NVD CVSS v3. EPSS exploit probability: 1.1%, top 39% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
10.0EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 10.0Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

remark-html is an open source nodejs library which compiles Markdown to HTML. In affected versions the documentation of remark-html has mentioned that it was safe by default. In practice the default was never safe and had to be opted into. That is, user input was not sanitized. This means arbitrary HTML can be passed through leading to potential XSS attacks. The problem has been patched in 13.0.2 and 14.0.1: remark-html is now safe by default, and the implementation matches the documentation. On older affected versions, pass sanitize: true if you cannot update.

CVSS v3
10.0
EG Score
10.0(medium)
EG Risk
50(Track)
EG Risk 50/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity100% × 45%
Exploitation1% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
1%
EPSS %ILE
62%
KEV
Not listed

Published

September 7, 2021

Last Modified

November 21, 2024

Advisory Details (3)

Auto-updated Jul 25, 2026
Patch available. Sources: github, github_commit, github_release.
github Patch Available

Unsafe defaults in `remark-html` · Advisory · remarkjs/remark-html · GitHub

Affected: 13.0.2 and 14.0.1:

https://github.com/remarkjs/remark-html/security/advisories/GHSA-9q5w-79cv-947m
github_release Patch Available

14.0.1

Patch available: remarkjs/remark-html 14.0.1

https://github.com/remarkjs/remark-html/releases/tag/14.0.1
github_commit Patch Available

commit b75c9dde582a (remarkjs/remark-html)

Patch available: remarkjs/remark-html 14.0.1 (contains commit b75c9dde582a)

https://github.com/remarkjs/remark-html/commit/b75c9dde582ad87ba498e369c033dc8a350478c1

Affected Packages

(1 across 1 ecosystem)
npm(1)
PackageVulnerable rangeFixed inDependents
remark-html14.0.014.0.1—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 12× in last 7d / 46× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 107 total refreshes for this CVE.

  1. 2026-07-26 14:52 UTCEPSS rescore
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Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2021-39199?
CVE-2021-39199 is a critical vulnerability published on September 7, 2021. remark-html is an open source nodejs library which compiles Markdown to HTML. In affected versions the documentation of remark-html has mentioned that it was safe by default. In practice the default was never safe and had to be opted into. That is, user input was not sanitized. This means arbitrary…
When was CVE-2021-39199 disclosed?
CVE-2021-39199 was first published in the National Vulnerability Database on September 7, 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-2021-39199 actively exploited?
CVE-2021-39199 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1% probability of exploitation in the next 30 days, which ranks it in the top 38.5% of all scored CVEs.
What is the CVSS score of CVE-2021-39199?
CVE-2021-39199 has a CVSS v3 base score of 10.0 (NVD).
How do I remediate CVE-2021-39199?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-39199, 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.

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