CVE-2021-29487
📋 TL;DR
CVE-2021-29487 is an authentication bypass vulnerability in October CMS that allows unauthenticated attackers to take over user accounts. Attackers need the Laravel secret key to exploit this vulnerability by crafting malicious requests. This affects frontend users of October CMS servers running vulnerable versions.
💻 Affected Systems
- October CMS
📦 What is this software?
October by Octobercms
October by Octobercms
⚠️ Risk & Real-World Impact
Worst Case
Complete account takeover of any frontend user, potentially leading to unauthorized access, data theft, privilege escalation, and full compromise of the CMS instance.
Likely Case
Targeted account takeover of specific users, potentially leading to unauthorized content modification, data access, or further attacks within the compromised account's permissions.
If Mitigated
Limited impact if Laravel secret key is properly secured and not accessible to attackers, though the vulnerability still exists in the codebase.
🎯 Exploit Status
Exploitation requires obtaining the Laravel secret key, which adds a barrier but is still feasible if the key is exposed or compromised through other means.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Build 472 or v1.1.5
Vendor Advisory: https://github.com/octobercms/october/security/advisories/GHSA-h76r-vgf3-j6w5
Restart Required: No
Instructions:
1. Update October CMS to Build 472 or v1.1.5. 2. For October CMS v1.0.x: Update to Build 472 via the dashboard or command line. 3. For October CMS v1.1.x: Update to v1.1.5 via composer: composer require october/system:v1.1.5. 4. Clear application cache if needed.
🔧 Temporary Workarounds
Secure Laravel Secret Key
linuxEnsure the Laravel secret key (APP_KEY in .env file) is properly secured and not accessible to unauthorized parties.
chmod 600 .env
chown www-data:www-data .env
Restrict Access to Frontend
allImplement network-level restrictions to limit access to the October CMS frontend to trusted users only.
🧯 If You Can't Patch
- Implement strict access controls and monitor for suspicious authentication attempts
- Regularly rotate Laravel secret keys and ensure they are never exposed in logs or error messages
🔍 How to Verify
Check if Vulnerable:
Check October CMS version via dashboard or by examining composer.lock file for october/system package version.Check Version:
php artisan october:versionVerify Fix Applied:
Verify version is Build 472 or higher for v1.0.x, or v1.1.5 or higher for v1.1.x. Check that the patched files from GitHub commits are present.📡 Detection & Monitoring
Log Indicators:
- Unusual authentication patterns
- Failed login attempts followed by successful logins from different IPs
- Requests with manipulated session/cookie data
Network Indicators:
- HTTP requests with specially crafted cookies or session data targeting October CMS endpoints
SIEM Query:
source="web_logs" AND (url_path="/account" OR url_path CONTAINS "october") AND (status_code=200 OR status_code=302) AND user_agent NOT IN expected_user_agents🔗 References
- https://github.com/octobercms/library/commit/016a297b1bec55d2e53bc889458ed2cb5c3e9374
- https://github.com/octobercms/library/commit/5bd1a28140b825baebe6becd4f7562299d3de3b9
- https://github.com/octobercms/october/security/advisories/GHSA-h76r-vgf3-j6w5
- https://github.com/octobercms/library/commit/016a297b1bec55d2e53bc889458ed2cb5c3e9374
- https://github.com/octobercms/library/commit/5bd1a28140b825baebe6becd4f7562299d3de3b9
- https://github.com/octobercms/october/security/advisories/GHSA-h76r-vgf3-j6w5
