CVE-2026-54525 — Markdown Preview Enhanced is a Markdown preview extension for Visual Studio Code.¶
Key facts
CVE-2026-54525 is a High (8.8) vulnerability: Markdown Preview Enhanced is a Markdown preview extension for Visual Studio Code.. This entry ships a detection-only PoC and a Docker test lab.
| CVE | CVE-2026-54525 |
| Severity | High (8.8) |
| Detection / prevention | — |
| PoC | poc.py |
| Source | 2026/CVE-2026-54525/ |
Details¶
English | 한국어
Description¶
Markdown Preview Enhanced is a Markdown preview extension for Visual Studio Code. Prior to 0.8.28, Markdown Preview Enhanced preview-link handling passes a decoded, Markdown-controlled link target to a Windows file-opening helper that invokes child_process.exec with the start command. When a Windows user opens an untrusted Markdown file and clicks a crafted external or unsupported-scheme link, shell metacharacters in the decoded target are interpreted by cmd.exe as command separators, allowing an attacker-selected command to run with the privileges of the current VS Code user. The attack requires one normal preview-link click but does not require malicious workspace configuration, script execution to be enabled, or additional files. This issue is fixed in version 0.8.28.
Vulnerability Details¶
| Property | Value |
|---|---|
| CVE ID | CVE-2026-54525 |
| Type | RCE |
| CVSS Score | 8.8 |
Proof of Concept¶
Download¶
# Download PoC script
curl -O https://raw.githubusercontent.com/fankh/vulnerability-poc/main/2026/CVE-2026-54525/poc.py
Usage¶
# Run PoC against target
python3 poc.py --target <TARGET_URL>
# With authentication
python3 poc.py --target <TARGET_URL> --username <USER> --password <PASS>
⚠️ Warning: This PoC is for authorized security testing only. It uses detection-only techniques and does not exploit or damage target systems.
Test Lab¶
This repository includes a Docker-based test environment with both vulnerable and patched applications.
Quick Start¶
# Clone and navigate to CVE directory
cd CVE-2026-54525
# Start both applications
docker-compose up -d
# Run tests
./run-tests.sh # Linux/Mac
./run-tests.ps1 # Windows PowerShell
Application Endpoints¶
| Application | URL | Status |
|---|---|---|
| Vulnerable App | http://localhost:8080 | Shows vulnerability |
| Patched App | http://localhost:8081 | Demonstrates fix |
Directory Structure¶
├── README.md # English documentation
├── README_KO.md # Korean documentation
├── poc.py # PoC detection script
├── docker-compose.yml # Container orchestration
├── run-tests.sh # Linux/Mac test runner
├── run-tests.ps1 # Windows test runner
├── vulnerable-app/ # Vulnerable version
│ ├── app.py
│ ├── Dockerfile
│ └── requirements.txt
└── patched-app/ # Fixed version
├── app.py
├── Dockerfile
└── requirements.txt
References¶
- https://github.com/shd101wyy/crossnote/commit/5588ca2121c3da43fe331575dc5cf4ef347b91ee
- https://github.com/shd101wyy/crossnote/pull/442
- https://github.com/shd101wyy/crossnote/releases/tag/0.9.29
- https://github.com/shd101wyy/vscode-markdown-preview-enhanced/commit/dcd80281c986293b93d9f1af34ced64dcb230c77
- https://github.com/shd101wyy/vscode-markdown-preview-enhanced/pull/2318
- https://github.com/shd101wyy/vscode-markdown-preview-enhanced/releases/tag/0.8.28
- https://github.com/shd101wyy/vscode-markdown-preview-enhanced/security/advisories/GHSA-7v6f-3vq6-r373
Generated by PoC Generator on 2026-10-15T07:59:22.956229245
Frequently asked questions¶
What is CVE-2026-54525?¶
CVE-2026-54525 is a High (8.8) vulnerability: Markdown Preview Enhanced is a Markdown preview extension for Visual Studio Code.. This entry ships a detection-only PoC and a Docker test lab.
How do I detect CVE-2026-54525?¶
Run the detection-only PoC included with this entry against your Docker test lab to confirm whether a target is affected; pair it with your own IDS logging.
How do I block or mitigate CVE-2026-54525?¶
Upgrade to a fixed version per the vendor advisory; the NVD record lists the affected versions. Use the included PoC to verify your remediation.
For authorized security testing and research only. See the full source and NVD record.