CVE-2026-27458
📋 TL;DR
This CVE describes a stored cross-site scripting (XSS) vulnerability in LinkAce's Atom feed endpoint for lists. An authenticated user can inject malicious payloads into list descriptions that execute arbitrary JavaScript in victims' browsers when they visit the feed URL. This affects all LinkAce instances running versions 2.4.2 or below.
💻 Affected Systems
- LinkAce
📦 What is this software?
Linkace by Linkace
⚠️ Risk & Real-World Impact
Worst Case
An authenticated attacker could steal session cookies, perform actions as authenticated users, redirect users to malicious sites, or compromise user accounts through client-side attacks.
Likely Case
Authenticated users with malicious intent could target other users who view the Atom feed, potentially stealing their session tokens or performing unauthorized actions.
If Mitigated
With proper input validation and output encoding, the vulnerability would be prevented, and only properly sanitized content would be displayed.
🎯 Exploit Status
The exploit requires authenticated access but is straightforward to execute once authenticated. The advisory includes technical details that could be used to create exploits.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2.4.3
Vendor Advisory: https://github.com/Kovah/LinkAce/security/advisories/GHSA-2r9p-95xj-p583
Restart Required: No
Instructions:
1. Backup your LinkAce installation and database. 2. Update to version 2.4.3 or later via git pull or package update. 3. Run database migrations if required. 4. Verify the fix by checking the version.
🔧 Temporary Workarounds
Disable Atom feeds
allTemporarily disable or block access to the /lists/feed endpoint to prevent exploitation.
# Add to web server configuration (nginx example)
location /lists/feed { return 403; }
# Or use .htaccess for Apache
RewriteRule ^lists/feed - [F]
Input validation filter
allImplement middleware or input filter to sanitize list descriptions containing CDATA-breaking sequences.
# PHP example for input sanitization
$description = str_replace(']]>', '', $description);
🧯 If You Can't Patch
- Implement strict input validation to reject or sanitize list descriptions containing ']]>' sequences.
- Restrict authenticated user permissions and implement principle of least privilege to limit potential attackers.
🔍 How to Verify
Check if Vulnerable:
Check if your LinkAce version is 2.4.2 or below. Test by creating a list with description containing ']]><script>alert(1)</script>' and checking if it executes in the Atom feed.Check Version:
php artisan --version | grep LinkAceVerify Fix Applied:
After updating to 2.4.3+, test the same payload. It should be properly escaped and not execute JavaScript.📡 Detection & Monitoring
Log Indicators:
- Unusual POST requests to list creation/update endpoints with XML/SVG payloads
- Multiple failed login attempts followed by list creation/modification
Network Indicators:
- Requests to /lists/feed with unusual user agents or referrers
- Outbound connections to suspicious domains after feed access
SIEM Query:
source="web_access_logs" AND (uri_path="/lists/feed" AND (user_agent="*script*" OR referrer="*malicious*"))