CVE-2022-27139
📋 TL;DR
CVE-2022-27139 is an arbitrary file upload vulnerability in Ghost CMS v4.39.0 that allows authenticated users to upload SVG files containing malicious JavaScript. This primarily affects Ghost administrators and trusted users who can upload files, potentially leading to client-side attacks against visitors viewing the SVG content.
💻 Affected Systems
- Ghost CMS
📦 What is this software?
Ghost by Ghost
⚠️ Risk & Real-World Impact
Worst Case
Trusted authenticated users could upload malicious SVG files containing JavaScript that executes in visitors' browsers, potentially leading to session hijacking, credential theft, or client-side attacks against website visitors.
Likely Case
Authenticated users with upload privileges could upload SVG files with embedded JavaScript that executes in visitors' browsers, potentially enabling cross-site scripting attacks against site visitors.
If Mitigated
If proper access controls are enforced and only trusted users have upload privileges, the impact is limited to client-side JavaScript execution within SVG files, which is intentional functionality according to the vendor.
🎯 Exploit Status
Exploitation requires authenticated access with file upload privileges. SVG files with embedded JavaScript can be uploaded and will execute in visitors' browsers.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: v4.39.1 and later
Vendor Advisory: http://ghost.org/docs/security/#privilege-escalation-attacks
Restart Required: Yes
Instructions:
1. Backup your Ghost installation and database. 2. Update Ghost to version 4.39.1 or later using npm update ghost. 3. Restart the Ghost service. 4. Verify the update was successful.
🔧 Temporary Workarounds
Restrict SVG upload permissions
allLimit file upload privileges to only essential, trusted administrators
Implement content security policy
allAdd CSP headers to restrict JavaScript execution from uploaded SVGs
🧯 If You Can't Patch
- Strictly limit file upload permissions to only essential, trusted administrators
- Implement web application firewall rules to block malicious SVG uploads
🔍 How to Verify
Check if Vulnerable:
Check Ghost version: if running v4.39.0, the system is vulnerableCheck Version:
ghost version or check package.json for Ghost versionVerify Fix Applied:
Verify Ghost version is 4.39.1 or later and test that SVG uploads are properly restricted📡 Detection & Monitoring
Log Indicators:
- Unusual SVG file uploads
- Multiple SVG upload attempts from single user
- Large or unusual SVG file sizes
Network Indicators:
- HTTP POST requests to upload endpoints with SVG content
- Unusual file upload patterns
SIEM Query:
source="ghost.log" AND ("upload" AND ".svg")