CVE-2026-54566

HIGHPre-NVD 8.58.5
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to the CVSS score beside it.

This high-severity CVE scores 8.5 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.3% (20th percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.

Triggered by: Headline CVSS from a secondary CVSS source
Sources: EPSS, a secondary CVSS source
Trending — 3 sources updated this weekElevated
8.5EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines at low or medium mission impact and sooner than that at high (the SSVC decision on this page).
  • CISA's Vulnrichment rates exploitation as PoC; EchelonGraph holds no exploit-code reference for it
CISA-KEV: Not listedEPSS PROB: 0.3%CVSS: 8.5Exploit: No code on recordExposed services: Not assessed

A fix is available — apply it.

Markdown Preview Enhanced is a Markdown preview extension for Visual Studio Code. Prior to 0.8.29, Markdown Preview Enhanced evaluates repository-controlled .crossnote/config.js and .crossnote/parser.js files with vm.runInNewContext, which does not provide a security boundary from the Node.js host realm. Opening a Markdown file in a malicious repository automatically loads these files, and prototype-chain traversal can reach the host Function constructor and process object, allowing operating-system commands to execute as the victim account without further interaction. Both configuration evaluation and parser-hook evaluation are affected, and the attack does not depend on module-scoped require being available. This issue is fixed in version 0.8.29.

CVSS v3
8.5
EG Score
8.5HIGHmedium confidence
EG Risk
54
EG Risk 54/100

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 (value × EchelonGraph’s weight)
Severity85% × 45%
The EG Score, 8.5 of 10.
Exploitation40% × 40%
EchelonGraph's fixed weight for EG-KEV Tier 3 (Elevated): a constant, not a probability.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low, Track* at medium and Attend at high mission impact.
Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
0.3%
EPSS %ILE
20th
KEV
Not listed

SSVC (CISA's decision table, applied by EchelonGraph)Track at low, Track* at medium and Attend at high mission impact.

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.

In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

October 14, 2026

Last Modified

October 16, 2026

Advisory Details (7)

Auto-updated Oct 14, 2026
🔬 Proof of concept available. Patch available. Sources: github, github_pr, github_commit, github_release.
GitHub release Patch Available

0.8.29

Patch available: shd101wyy/vscode-markdown-preview-enhanced 0.8.29

https://github.com/shd101wyy/vscode-markdown-preview-enhanced/releases/tag/0.8.29
GitHub release Patch Available

0.9.30

Patch available: shd101wyy/crossnote 0.9.30

https://github.com/shd101wyy/crossnote/releases/tag/0.9.30
GitHub commit Patch Available

commit 0d4010988c6a (shd101wyy/vscode-markdown-preview-enhanced)

Patch available: shd101wyy/vscode-markdown-preview-enhanced 0.8.29 (contains commit 0d4010988c6a)

https://github.com/shd101wyy/vscode-markdown-preview-enhanced/commit/0d4010988c6ae56a38c6dec4a7509cbd5a7dcb4c
GitHub commit Patch Available

commit e4890d64502e (shd101wyy/crossnote)

Patch available: shd101wyy/crossnote 0.9.30 (contains commit e4890d64502e)

https://github.com/shd101wyy/crossnote/commit/e4890d64502e53b717cce0cb73f1a78b244dc640
GitHub pull request Patch Available

0.8.29

Patch available: shd101wyy/vscode-markdown-preview-enhanced 0.8.29 (PR #2320 merged 2026-06-06)

https://github.com/shd101wyy/vscode-markdown-preview-enhanced/pull/2320
GitHub pull request Patch Available

0.9.30: security (config/parser RCE sandbox) + heading-ID and @import fixes

Patch available: shd101wyy/crossnote 0.9.30 (PR #443 merged 2026-06-06)

https://github.com/shd101wyy/crossnote/pull/443
GitHub advisoryMentions a patch (unverified)🟡 PoC Available

Remote Code Execution via VM Sandbox Escape in `.crossnote/config.js` and `.crossnote/parser.js` · Advisory · shd101wyy/vscode-markdown-preview-enhanced · GitHub

https://github.com/shd101wyy/vscode-markdown-preview-enhanced/security/advisories/GHSA-427h-jhpr-8jch

Weakness Classification(1)

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

Data Freshness Timeline

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

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. 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. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

  1. 2026-10-16 16:42 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  2. 2026-10-16 16:10 UTCEG score recompute
  3. 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  4. 2026-10-14 20:27 UTCEG score recompute
  5. 2026-10-14 19:56 UTCEG score recompute
  6. 2026-10-14 19:28 UTCEG score recomputeFirst assessed: 8.5 HIGH
  7. 2026-10-14 19:24 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-54566?
CVE-2026-54566 is a high-severity vulnerability; its CVE record was published on October 14, 2026. Markdown Preview Enhanced is a Markdown preview extension for Visual Studio Code. Prior to 0.8.29, Markdown Preview Enhanced evaluates repository-controlled .crossnote/config.js and .crossnote/parser.js files with vm.runInNewContext, which does not provide a security boundary from the Node.js host…
When was the CVE record for CVE-2026-54566 published?
The CVE record for CVE-2026-54566 was published on October 14, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of October 16, 2026; the record at its source may have been updated since.
Is CVE-2026-54566 actively exploited?
CVE-2026-54566 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.3% probability of exploitation in the next 30 days (20th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-54566?
CVE-2026-54566 has a CVSS base score of 8.5 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-54566?
A fix for CVE-2026-54566 is available: update to the fixed version the vendor names in its advisory.

Dependency Blast Radius

Explore the affected products and dependency analysis for CVE-2026-54566

Explore →

Is Your Infrastructure Affected by CVE-2026-54566?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.