Sandbox escape in Markdown Preview Enhanced allows code execution
Key facts
- Attack vector
- Local
- Privileges required
- None
- User interaction
- Passive
- Attack complexity
- Low
- Attack requirements
- None
- Impact type
- Code execution
- Confidentiality · integrity · availability
- High · High · High
- Fix status
- Fixed
Attack profile from CVSS 4.0 · CNA. Fix status from CNA. Impact type from CWE-94.
Summary
The shd101wyy vscode-markdown-preview-enhanced extension before 0.8.29 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 (CWE-94). Opening a Markdown file in a malicious repository loads these files automatically, and an attacker can reach host objects to run operating system commands as the victim account without further interaction.
Written with Claude Haiku 5.5 from the sources below · 2026-10-28
Description from the CNA
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.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- Poc
- Automatable
- No
- Technical impact
- Total
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
Remediation
Update shd101wyy vscode-markdown-preview-enhanced to version 0.8.29, which fixes the issue.
Written with Claude Haiku 5.5 from the sources below · 2026-10-28
- Fix · CNA vscode-markdown-preview-enhanced (shd101wyy) Fixed in 0.8.29
Timeline
- 2026-10-15 Threatist record created from CVE-2026-54566
References
Other 7
- https://github.com/shd101wyy/vscode-markdown-preview-enhanced/security/advisories/GHSA-427h-jhpr-8jch
- https://github.com/shd101wyy/crossnote/pull/443
- https://github.com/shd101wyy/vscode-markdown-preview-enhanced/pull/2320
- https://github.com/shd101wyy/crossnote/commit/e4890d64502e53b717cce0cb73f1a78b244dc640
- https://github.com/shd101wyy/vscode-markdown-preview-enhanced/commit/0d4010988c6ae56a38c6dec4a7509cbd5a7dcb4c
- https://github.com/shd101wyy/crossnote/releases/tag/0.9.30
- https://github.com/shd101wyy/vscode-markdown-preview-enhanced/releases/tag/0.8.29
More shd101wyy vulnerabilities
- TI-2025-40425 An issue in Visual Studio Code Extensions Markdown Preview Enhanced v0.8.18 allows… CVSS 3.1HIGH 8.8
- TI-2026-37396 Markdown Preview Enhanced Arbitrary Code Execution via WaveDrom eval() CVSS 4.0HIGH 8.6
- TI-2026-09857 Markdown Preview Enhanced 0.8.x Code Injection via WaveDrom Rendering CVSS 4.0HIGH 8.4
- TI-2026-74455 Unvalidated command dispatch in Markdown Preview Enhanced extension CVSS 4.0HIGH 7.3
- TI-2026-74454 Cross-site scripting in Markdown Preview Enhanced VS Code extension CVSS 4.0MEDIUM 6.9
- TI-2026-74456 Arbitrary file write in Markdown Preview Enhanced for VS Code CVSS 4.0MEDIUM 5.8
Sources
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences