CVE-2024-56508
📋 TL;DR
LinkAce versions before 1.15.6 contain a file upload vulnerability in the 'Import Bookmarks' feature that allows attackers to upload malicious HTML files containing JavaScript payloads. When users access these uploaded links, the JavaScript executes, potentially leading to cross-site scripting (XSS) attacks. This affects all self-hosted LinkAce instances running vulnerable versions.
💻 Affected Systems
- LinkAce
📦 What is this software?
Linkace by Linkace
⚠️ Risk & Real-World Impact
Worst Case
Attackers could steal session cookies, perform actions as authenticated users, deface the application, or redirect users to malicious sites, potentially leading to complete account compromise.
Likely Case
Attackers would typically use this to steal session cookies or credentials, perform limited actions as the victim user, or deliver malware through malicious redirects.
If Mitigated
With proper input validation and content security policies, the impact would be limited to minor UI manipulation or blocked script execution.
🎯 Exploit Status
Exploitation requires the attacker to have access to upload bookmarks, which typically requires authentication. However, once uploaded, the payload executes when any user accesses the link.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 1.15.6
Vendor Advisory: https://github.com/Kovah/LinkAce/security/advisories/GHSA-2wvv-4576-8862
Restart Required: Yes
Instructions:
1. Backup your LinkAce database and files. 2. Update LinkAce to version 1.15.6 or later using your preferred update method (composer update, git pull, or manual download). 3. Run database migrations if required. 4. Restart your web server.
🔧 Temporary Workarounds
Disable Import Bookmarks Feature
allTemporarily disable the Import Bookmarks functionality to prevent file uploads until patching is complete.
Edit your LinkAce configuration to remove or disable the import feature. This typically involves modifying the application's routes or middleware.
Implement Content Security Policy
allAdd a strict Content Security Policy header to block inline JavaScript execution.
Add 'Content-Security-Policy: script-src 'self'' to your web server configuration or application headers.
🧯 If You Can't Patch
- Restrict access to the Import Bookmarks feature to trusted administrators only.
- Implement web application firewall rules to block uploads of HTML files containing JavaScript.
🔍 How to Verify
Check if Vulnerable:
Check your LinkAce version. If it's below 1.15.6, you are vulnerable. Also test by attempting to upload an HTML file with JavaScript via the Import Bookmarks feature.Check Version:
Check the LinkAce admin dashboard or run 'composer show kovah/linkace' in the installation directory.Verify Fix Applied:
After updating to 1.15.6 or later, verify that HTML files with JavaScript payloads are properly sanitized or rejected when uploaded through the Import Bookmarks feature.📡 Detection & Monitoring
Log Indicators:
- Unusual file uploads via the Import Bookmarks endpoint
- HTML files with script tags being processed
- Multiple failed import attempts
Network Indicators:
- HTTP POST requests to /api/v1/import or similar import endpoints with HTML content
- Unusual traffic patterns to bookmark links
SIEM Query:
source="web_server" AND (uri_path="/api/v1/import" OR uri_path LIKE "%/import%") AND (file_extension="html" OR content_type="text/html")