CVE-2023-36091
📋 TL;DR
This CVE describes an authentication bypass vulnerability in D-Link DIR-895 routers running firmware version FW102b07. Remote attackers can exploit a flaw in the phpcgi_main function to gain escalated privileges without valid credentials. Only unsupported D-Link products are affected.
💻 Affected Systems
- D-Link DIR-895
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of the router allowing attackers to intercept all network traffic, install persistent malware, pivot to internal networks, and disable security controls.
Likely Case
Attackers gain administrative access to the router, change DNS settings for phishing, disable firewall rules, and monitor network activity.
If Mitigated
With proper network segmentation and access controls, impact is limited to the router itself rather than the entire network.
🎯 Exploit Status
The vulnerability allows unauthenticated access via the web interface. Exploitation likely requires sending crafted requests to the vulnerable CGI endpoint.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: N/A
Vendor Advisory: https://www.dlink.com/en/security-bulletin/
Restart Required: No
Instructions:
No official patch available since product is end-of-life. Replace affected hardware with supported equipment.
🔧 Temporary Workarounds
Disable Remote Management
allDisable WAN-side access to the router's administrative interface
Access router admin panel > Advanced > Remote Management > Disable
Network Segmentation
allIsolate the router from critical internal networks using VLANs or separate physical networks
🧯 If You Can't Patch
- Replace affected D-Link DIR-895 routers with currently supported hardware
- Implement strict firewall rules to block all external access to the router's administrative interface (ports 80, 443, 8080)
🔍 How to Verify
Check if Vulnerable:
Check router firmware version in admin interface: System > Firmware. If version is FW102b07, device is vulnerable.Check Version:
N/A - Check via web interface at http://router_ip/ or via serial consoleVerify Fix Applied:
Since no patch exists, verification requires replacing hardware or implementing workarounds and testing that remote administrative access is blocked.📡 Detection & Monitoring
Log Indicators:
- Unusual authentication attempts to router admin interface
- Successful admin logins from unexpected IP addresses
- Configuration changes without authorized user activity
Network Indicators:
- HTTP requests to /cgi-bin/phpcgi_main or similar CGI endpoints
- Traffic to router administrative ports from external IPs
SIEM Query:
source="router_logs" AND (event="admin_login" OR url="*cgi-bin*phpcgi*")