CVE-2020-27514
📋 TL;DR
CVE-2020-27514 is a directory traversal vulnerability in ZrLog's admin API that allows remote attackers to delete arbitrary files on the server. This can lead to denial of service by deleting critical system files. All ZrLog installations running version 2.1.15 are affected.
💻 Affected Systems
- ZrLog
📦 What is this software?
Zrlog by Zrlog
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise through deletion of critical OS files, leading to permanent data loss and system unavailability.
Likely Case
Deletion of web application files causing service disruption, loss of website content, and potential data corruption.
If Mitigated
Limited impact if proper file permissions and web server sandboxing are implemented, though service disruption is still possible.
🎯 Exploit Status
Exploitation requires sending crafted HTTP requests to the vulnerable endpoint with directory traversal sequences.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2.1.16 or later
Vendor Advisory: https://github.com/94fzb/zrlog/issues/66
Restart Required: Yes
Instructions:
1. Backup your ZrLog installation and database. 2. Download and install ZrLog version 2.1.16 or later from the official repository. 3. Restart the web server or application service. 4. Verify the fix by checking the version and testing the vulnerable endpoint.
🔧 Temporary Workarounds
Restrict Admin API Access
allBlock access to the vulnerable admin API endpoint using web server configuration or firewall rules.
# For Apache: RewriteRule ^/admin/api/TemplateController - [F]
# For Nginx: location ~ /admin/api/TemplateController { deny all; }
File Permission Hardening
linuxSet restrictive file permissions on critical system directories outside the web root.
chmod 700 /etc /usr /var
chmod 755 /path/to/zrlog
🧯 If You Can't Patch
- Implement strict network segmentation to isolate ZrLog instances from critical systems.
- Deploy web application firewall (WAF) with directory traversal protection rules.
🔍 How to Verify
Check if Vulnerable:
Check if ZrLog version is 2.1.15 by examining the application files or admin panel.Check Version:
grep -r 'version' /path/to/zrlog/install/*.propertiesVerify Fix Applied:
Verify installation of version 2.1.16 or later and test that directory traversal attempts to delete files are blocked.📡 Detection & Monitoring
Log Indicators:
- HTTP requests containing '../' sequences to admin API endpoints
- File deletion operations on unexpected paths in system logs
Network Indicators:
- HTTP POST/PUT requests to /admin/api/TemplateController with path traversal payloads
SIEM Query:
source="web_logs" AND uri="/admin/api/TemplateController" AND (payload="../" OR payload="..\\")