CVE-2026-54566

8.5High

Published 14 Oct 2026 · NVD status: Awaiting Analysis · AI triage by gemini-3.8-flash

8.5High

Attack vector: Local
Complexity: Low
Privileges needed: None
User interaction: Passive
Impact: Full C/I/A compromise
Weakness: CWE-94

Impact

Attackers can achieve arbitrary code execution under your local user account when you open a Markdown file in a malicious repository. The attack requires tricking a user into opening an untrusted workspace containing crafted configuration or parser scripts.

Root cause

The extension executes repository-controlled JavaScript files using Node's vm.runInNewContext, allowing prototype-chain breakout into the host environment.

Affected systems

Markdown Preview Enhanced for VS Code prior to version 0.8.29

CVSS v4.0 · CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Fix & remediation

Upgrade the Markdown Preview Enhanced extension to version 0.8.29 or later. If updating immediately is not possible, disable the extension when opening untrusted repositories.

shell

$ code --install-extension shd101wyy.markdown-preview-enhanced --force

AI-suggested. Run it in staging first and check it against the vendor advisory. Why?

Ad · In-content banner

NVD description

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.

References

Source: nvd.nist.gov/vuln/detail/CVE-2026-54566