Markdown Preview Enhanced: Remote Code Execution via VM Sandbox Escape in `.crossnote/config.js` and `.crossnote/parser.js`

published 2026-10-14 25 d ago modified 2026-10-16 23 d ago also EUVD-2026-101582

cvss: 8.5; version 4.0, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.3%; EPSS 0.3% chance of exploitation in 30 days, percentile 22%
public exploits: 0; none known

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.

Patch / fix

links 6

github.com/shd101wyy/crossnote@e4890d6 commit
github.com/shd101wyy/vscode-markdown-preview-enhanced@0d40109 commit
github.com/shd101wyy/crossnote#443 pull request
github.com/shd101wyy/vscode-markdown-preview-enhanced#2320 pull request
github.com/shd101wyy/crossnote/releases/tag/0.9.30 release
github.com/shd101wyy/vscode-markdown-preview-enhanced/releases/tag/0.… release

CISA SSVC

Exploitation: Proof of concept is public
Automatable: no
Technical impact: total
Assessed: 25 d ago (2026-10-14)

Exploit prediction

0.30% chance of exploitation in the next 30 days, higher than 22% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

github.com https://github.com/shd101wyy/vscode-markdown-preview-enhanced/security/advisories/GHSA-427h-jhpr-8jch referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
CNA	4.0	8.5	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
CNA	4.0	8.5	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

Affected products

shd101wyy vscode-markdown-preview-enhanced

Classification

Weakness

CWE-94 Improper Control of Generation of Code

References

Sources

CVE List CVE-2026-54566
NVD CVE-2026-54566

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary