CVE-2025-43879
📋 TL;DR
This critical vulnerability allows remote unauthenticated attackers to execute arbitrary operating system commands on affected ELECOM WRH-733GBK and WRH-733GWH routers via the telnet function. Attackers can gain complete control of the device, potentially compromising the entire network. All users of these specific router models are affected.
💻 Affected Systems
- ELECOM WRH-733GBK
- ELECOM WRH-733GWH
⚠️ Manual Verification Required
This CVE does not have specific version information in our database, so automatic vulnerability detection cannot determine if your system is affected.
Why? The CVE database entry doesn't specify which versions are vulnerable (no version ranges provided by the vendor/NVD).
🔒 Custom verification scripts are available for registered users. Sign up free to download automated test scripts.
- Review the CVE details at NVD
- Check vendor security advisories for your specific version
- Test if the vulnerability is exploitable in your environment
- Consider updating to the latest version as a precaution
⚠️ Risk & Real-World Impact
Worst Case
Complete device takeover leading to network compromise, data exfiltration, ransomware deployment, and use as a pivot point for attacking other internal systems.
Likely Case
Router compromise allowing traffic interception, credential theft, DNS hijacking, and installation of persistent backdoors.
If Mitigated
Limited impact if routers are behind firewalls with strict inbound filtering and telnet is disabled.
🎯 Exploit Status
The vulnerability requires sending specially crafted requests to the telnet service, which is straightforward for attackers with network access.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check ELECOM advisory for specific firmware version
Vendor Advisory: https://www.elecom.co.jp/news/security/20250624-02/
Restart Required: Yes
Instructions:
1. Access router web interface. 2. Navigate to firmware update section. 3. Download latest firmware from ELECOM website. 4. Upload and apply firmware update. 5. Reboot router.
🔧 Temporary Workarounds
Disable Telnet Service
allCompletely disable the telnet service to prevent exploitation.
Access router admin interface -> Network Services -> Disable Telnet
Network Access Control
linuxRestrict access to telnet port (TCP 23) using firewall rules.
iptables -A INPUT -p tcp --dport 23 -j DROP
🧯 If You Can't Patch
- Isolate affected routers in separate VLAN with strict network segmentation
- Implement network monitoring for unusual telnet traffic patterns
🔍 How to Verify
Check if Vulnerable:
Check if telnet service is running on port 23 and router model matches affected products.Check Version:
Check router web interface or use telnet/ssh to query firmware versionVerify Fix Applied:
Verify firmware version matches patched version from vendor advisory and telnet service is either disabled or updated.📡 Detection & Monitoring
Log Indicators:
- Unusual telnet connection attempts
- Failed authentication attempts on telnet
- Unexpected command execution in system logs
Network Indicators:
- Telnet traffic to router from unexpected sources
- Unusual outbound connections from router
SIEM Query:
source="router_logs" AND (port=23 OR service="telnet") AND (status="success" OR command="*" )