CVE-2026-2615
📋 TL;DR
This CVE-2026-2615 is a command injection vulnerability in Wavlink WL-NU516U1 routers that allows remote attackers to execute arbitrary commands on affected devices. The vulnerability exists in the singlePortForwardDelete function of the firewall.cgi script where the del_flag parameter is not properly sanitized. All users of Wavlink WL-NU516U1 routers with firmware up to 20251208 are affected.
💻 Affected Systems
- Wavlink WL-NU516U1
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete device compromise allowing attacker to install persistent backdoors, steal credentials, pivot to internal networks, or use device as botnet member.
Likely Case
Remote code execution leading to device takeover, network traffic interception, or denial of service.
If Mitigated
Limited impact if device is behind firewall with restricted WAN access and proper network segmentation.
🎯 Exploit Status
Exploit code is publicly available on GitHub, making this easily weaponizable by attackers.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: None available - vendor did not respond to disclosure
Restart Required: No
Instructions:
No official patch available. Monitor vendor website for firmware updates.
🔧 Temporary Workarounds
Block CGI endpoint access
linuxUse firewall rules to block access to the vulnerable /cgi-bin/firewall.cgi endpoint
iptables -A INPUT -p tcp --dport 80 -m string --string "/cgi-bin/firewall.cgi" --algo bm -j DROP
iptables -A INPUT -p tcp --dport 443 -m string --string "/cgi-bin/firewall.cgi" --algo bm -j DROP
Disable port forwarding feature
allDisable the single port forwarding feature if not required
🧯 If You Can't Patch
- Isolate affected devices in separate VLAN with strict network segmentation
- Implement strict egress filtering to prevent compromised devices from reaching external C2 servers
🔍 How to Verify
Check if Vulnerable:
Check firmware version via router web interface or SSH if available. If version is 20251208 or earlier, device is vulnerable.Check Version:
Check router web interface at http://[router-ip]/ or via SSH if enabled: cat /etc/versionVerify Fix Applied:
No official fix available to verify. If vendor releases update, install and confirm version is newer than 20251208.📡 Detection & Monitoring
Log Indicators:
- Unusual CGI requests to /cgi-bin/firewall.cgi with shell metacharacters
- Suspicious command execution in router logs
- Multiple failed authentication attempts followed by CGI access
Network Indicators:
- HTTP POST requests to /cgi-bin/firewall.cgi with shell commands in parameters
- Outbound connections from router to unknown IPs
SIEM Query:
source="router_logs" AND (uri="/cgi-bin/firewall.cgi" AND (param="del_flag" AND value MATCH "[;&|`$()]"))