CVE-2026-54566
HIGH 8.5Markdown 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.
Severe if exploited (CVSS 8.5), but no known exploitation and low modeled probability. Patch on a normal cadence.
Exploitation likelihood
0.3%chance of exploitation in 30 days · 22nd percentile
Impact if exploited
8.5CVSS 4.0 · HIGH
- ConfidentialityHigh
- IntegrityHigh
- AvailabilityHigh
What an attacker needs
- ⚠Access: Requires local access to the host
- ✓Privileges: No account or privileges required
- ⚠User interaction: Succeeds with passive user activity
- ✓Complexity: No special conditions — reliably repeatable
- ✓Requirements: No special attack requirements
✓ lowers the bar for an attacker · ⚠ raises it
Proof of concept
No public PoC is currently catalogued.
Search for new PoCs
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Tracked sources are checked daily for recent CVEs, including PoCs published after the original disclosure. A later release appears after a tracked source lists it and a refresh succeeds.
Data snapshot:
Weakness (CWE)
- CWE-94: : Improper Control of Generation of Code ('Code Injection')
CVSS vector
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
References and research data (JSON)
All CVSS metrics
- HIGH 8.5 v4.0 · CNA Primary
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 - HIGH 8.5 v4.0 · NVD Secondary
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
References
Exploit-tagged references (not proof of a PoC)
- https://github.com/shd101wyy/vscode-markdown-preview-enhanced/security/advisories/GHSA-427h-jhpr-8jch CVE record · GitHub_M · Updated 2026-10-14T19:08:43.663Z
CVE record · CISA-ADP · Updated 2026-10-14T19:45:22.736Z
NVD · CVE-2026-54566 · Updated 2026-10-16T16:00:33.533
Advisories
- https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-101582 EUVD · EUVD-2026-101582
Technical & other
- https://github.com/shd101wyy/crossnote/pull/443 CVE record · GitHub_M · Updated 2026-10-14T19:08:43.663Z
NVD · CVE-2026-54566 · Updated 2026-10-16T16:00:33.533 - https://github.com/shd101wyy/vscode-markdown-preview-enhanced/pull/2320 CVE record · GitHub_M · Updated 2026-10-14T19:08:43.663Z
NVD · CVE-2026-54566 · Updated 2026-10-16T16:00:33.533 - https://github.com/shd101wyy/crossnote/commit/e4890d64502e53b717cce0cb73f1a78b244dc640 CVE record · GitHub_M · Updated 2026-10-14T19:08:43.663Z
NVD · CVE-2026-54566 · Updated 2026-10-16T16:00:33.533 - https://github.com/shd101wyy/vscode-markdown-preview-enhanced/commit/0d4010988c6ae56a38c6dec4a7509cbd5a7dcb4c CVE record · GitHub_M · Updated 2026-10-14T19:08:43.663Z
NVD · CVE-2026-54566 · Updated 2026-10-16T16:00:33.533 - https://github.com/shd101wyy/crossnote/releases/tag/0.9.30 CVE record · GitHub_M · Updated 2026-10-14T19:08:43.663Z
NVD · CVE-2026-54566 · Updated 2026-10-16T16:00:33.533 - https://github.com/shd101wyy/vscode-markdown-preview-enhanced/releases/tag/0.8.29 CVE record · GitHub_M · Updated 2026-10-14T19:08:43.663Z
NVD · CVE-2026-54566 · Updated 2026-10-16T16:00:33.533