CVE-2025-57685
📋 TL;DR
This vulnerability allows unauthenticated attackers to execute arbitrary commands with highest privileges on affected LB-Link routers. Attackers can exploit the /goform/set_serial_cfg interface to gain complete control of the device. All users of the listed LB-Link router models are affected.
💻 Affected Systems
- LB-Link BL-AC2100_AZ3
- BL-WR4000
- BL-WR9000_AE4
- BL-AC1900_AZ2
- BL-X26_AC8
- BL-LTE300_DA4
⚠️ 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 enabling attackers to install persistent malware, intercept all network traffic, pivot to internal networks, and use the router as part of a botnet.
Likely Case
Router compromise leading to network surveillance, credential theft, DNS hijacking, and use in DDoS attacks.
If Mitigated
Limited impact if routers are behind firewalls with strict inbound filtering, though internal threats remain.
🎯 Exploit Status
Public exploit documentation exists on GitHub. The vulnerability requires no authentication and has simple exploitation steps.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: https://www.b-link.net.cn/
Restart Required: Yes
Instructions:
1. Check vendor website for firmware updates. 2. Download appropriate firmware for your model. 3. Access router admin interface. 4. Navigate to firmware upgrade section. 5. Upload and apply new firmware. 6. Reboot router.
🔧 Temporary Workarounds
Block Access to Vulnerable Interface
linuxUse firewall rules to block access to the /goform/set_serial_cfg endpoint
iptables -A INPUT -p tcp --dport 80 -m string --string "/goform/set_serial_cfg" --algo bm -j DROP
iptables -A INPUT -p tcp --dport 443 -m string --string "/goform/set_serial_cfg" --algo bm -j DROP
Disable Remote Administration
allTurn off remote management features on the router
🧯 If You Can't Patch
- Isolate affected routers in separate VLAN with strict firewall rules
- Implement network segmentation to limit lateral movement from compromised routers
🔍 How to Verify
Check if Vulnerable:
Attempt to access http://[router-ip]/goform/set_serial_cfg with a crafted payload. Monitor for command execution responses.Check Version:
Login to router admin interface and check firmware version in system status or about page.Verify Fix Applied:
After patching, attempt the same exploit and verify it no longer executes commands. Check firmware version matches patched release.📡 Detection & Monitoring
Log Indicators:
- HTTP requests to /goform/set_serial_cfg with command injection patterns
- Unusual system command execution in router logs
- Multiple failed login attempts followed by successful access to admin interfaces
Network Indicators:
- Unusual outbound connections from router to unknown IPs
- DNS queries to suspicious domains from router
- Unexpected port scans originating from router
SIEM Query:
source="router_logs" AND (url="/goform/set_serial_cfg" OR command="*sh*" OR command="*cmd*")