CVE-2021-41126
📋 TL;DR
This vulnerability allows deleted administrator accounts to still authenticate and access the October CMS backend. It affects October CMS v2.0 installations where administrator accounts have been deleted. The issue stems from improper authentication validation.
💻 Affected Systems
- October CMS
📦 What is this software?
October by Octobercms
⚠️ Risk & Real-World Impact
Worst Case
Deleted administrators regain full backend access, potentially compromising the entire CMS, modifying content, installing malicious plugins, or accessing sensitive data.
Likely Case
Former administrators who were deleted could sign in and perform unauthorized actions within the CMS backend, leading to data manipulation or privilege escalation.
If Mitigated
With proper access logging and monitoring, unauthorized logins could be detected and blocked, limiting damage to logged activities.
🎯 Exploit Status
Exploitation requires knowledge of deleted administrator credentials. No public exploit code is known, but the vulnerability is straightforward to leverage.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: v2.1.12
Vendor Advisory: https://github.com/octobercms/october/security/advisories/GHSA-6gjf-7w99-j7x7
Restart Required: No
Instructions:
1. Backup your October CMS installation and database. 2. Update the october/october package to version 2.1.12 via Composer: composer require october/october:2.1.12. 3. Run any necessary migrations: php artisan october:up. 4. Verify the update by checking the version in the backend.
🔧 Temporary Workarounds
No workarounds available
allThe vendor states there are no workarounds for this issue. Updating is the only solution.
🧯 If You Can't Patch
- Monitor authentication logs for any login attempts from deleted administrator accounts and block them manually.
- Implement additional authentication controls like IP whitelisting or multi-factor authentication for the backend.
🔍 How to Verify
Check if Vulnerable:
Check if you are running October CMS v2.0 and have deleted any administrator accounts. Attempt to sign in with credentials of a deleted administrator account.Check Version:
php artisan october:versionVerify Fix Applied:
After updating to v2.1.12, attempt to sign in with credentials of a deleted administrator account; it should fail. Verify the version in the backend matches 2.1.12.📡 Detection & Monitoring
Log Indicators:
- Successful login events from previously deleted administrator accounts in October CMS logs or authentication logs.
Network Indicators:
- Unusual backend access patterns from IP addresses associated with former administrators.
SIEM Query:
source="october.log" AND "successful login" AND user IN [list_of_deleted_admins]