📄 Description (English)
A weakness has been identified in Wavlink WL-NU516U1 260227. This vulnerability affects the function ftext of the file /cgi-bin/nas.cgi. This manipulation of the argument Content-Length causes stack-based buffer overflow. The attack can be initiated remotely. The exploit has been made available to the public and could be used for attacks. The vendor was contacted early about this disclosure but did not respond in any way.
🤖 AI Executive Summary
CVE-2026-4861 is a critical stack-based buffer overflow vulnerability in Wavlink WL-NU516U1 network storage devices affecting the /cgi-bin/nas.cgi endpoint. The vulnerability can be exploited remotely by manipulating the Content-Length parameter, potentially allowing unauthenticated remote code execution. With no patch available and the vendor unresponsive, this poses an immediate threat to organizations using affected Wavlink NAS devices.
📄 Description (Arabic)
🤖 AI Intelligence Analysis Analyzed: Apr 23, 2026 11:52
🇸🇦 Saudi Arabia Impact Assessment
This vulnerability poses significant risk to Saudi organizations in multiple sectors: (1) Banking/SAMA-regulated entities using Wavlink NAS for backup and archival systems; (2) Government agencies (NCA, CITC) storing sensitive data on network storage; (3) Healthcare institutions (MOH, private hospitals) maintaining patient records; (4) Energy sector (ARAMCO, utilities) using NAS for operational technology backups; (5) Telecommunications (STC, Mobily) for network infrastructure data storage. The unpatched nature and public exploit availability make this an immediate threat requiring urgent action.
🏢 Affected Saudi Sectors
Banking and Financial Services
Government and Public Administration
Healthcare and Medical Institutions
Energy and Utilities
Telecommunications
Education
Manufacturing
🎯 MITRE ATT&CK Techniques
⚖️ Saudi Risk Score (AI)
9.2
/ 10.0
🔧 Remediation Steps (English)
IMMEDIATE ACTIONS:
1. Identify all Wavlink WL-NU516U1 devices in your network using network scanning tools (nmap, Shodan queries)
2. Isolate affected devices from production networks immediately or restrict network access to trusted sources only
3. Disable remote access to the /cgi-bin/nas.cgi endpoint if possible through firewall rules
4. Change all administrative credentials for affected devices
5. Review access logs for suspicious Content-Length manipulation attempts
COMPENSATING CONTROLS:
1. Implement network segmentation - place NAS devices on isolated VLAN with strict ACLs
2. Deploy WAF/IPS rules to block malformed Content-Length headers to /cgi-bin/nas.cgi
3. Monitor for exploitation attempts: Log all HTTP requests with abnormal Content-Length values
4. Implement rate limiting on CGI endpoints
5. Consider replacing affected Wavlink devices with alternative vendors (QNAP, Synology, NetApp) that provide security updates
DETECTION RULES:
1. IDS/IPS: Alert on POST/GET requests to /cgi-bin/nas.cgi with Content-Length > 1024 bytes
2. WAF: Block requests with Content-Length mismatches or stack-suspicious payloads
3. SIEM: Create correlation rules for multiple failed attempts to /cgi-bin/nas.cgi
4. Endpoint: Monitor for unexpected process spawning from Wavlink device processes
🔧 خطوات المعالجة (العربية)
الإجراءات الفورية:
1. تحديد جميع أجهزة Wavlink WL-NU516U1 في شبكتك باستخدام أدوات المسح (nmap، استعلامات Shodan)
2. عزل الأجهزة المتأثرة عن شبكات الإنتاج فوراً أو تقييد الوصول إلى الشبكة من مصادر موثوقة فقط
3. تعطيل الوصول البعيد إلى نقطة نهاية /cgi-bin/nas.cgi إن أمكن من خلال قواعد جدار الحماية
4. تغيير جميع بيانات اعتماد المسؤول للأجهزة المتأثرة
5. مراجعة سجلات الوصول للمحاولات المريبة للتلاعب بـ Content-Length
الضوابط التعويضية:
1. تنفيذ تقسيم الشبكة - ضع أجهزة NAS على VLAN معزول مع قوائم تحكم وصول صارمة
2. نشر قواعد WAF/IPS لحظر رؤوس Content-Length المشوهة إلى /cgi-bin/nas.cgi
3. مراقبة محاولات الاستغلال: تسجيل جميع طلبات HTTP برؤوس Content-Length غير عادية
4. تنفيذ تحديد معدل على نقاط نهاية CGI
5. النظر في استبدال أجهزة Wavlink المتأثرة ببدائل من البائعين الآخرين (QNAP، Synology، NetApp)
قواعد الكشف:
1. IDS/IPS: تنبيه على طلبات POST/GET إلى /cgi-bin/nas.cgi مع Content-Length > 1024 بايت
2. WAF: حظر الطلبات ذات عدم تطابق Content-Length أو الحمولات المريبة
3. SIEM: إنشاء قواعد ارتباط للمحاولات المتعددة الفاشلة إلى /cgi-bin/nas.cgi
4. نقطة النهاية: مراقبة توليد العمليات غير المتوقعة من عمليات جهاز Wavlink
📋 Regulatory Compliance Mapping
🟢 NCA ECC 2024
ECC 2024 A.12.6.1 - Management of technical vulnerabilities
ECC 2024 A.14.2.1 - Secure development policy
ECC 2024 A.12.3.1 - Configuration management
ECC 2024 A.13.1.3 - Segregation of networks
🔵 SAMA CSF
ID.RA-1 - Asset management and vulnerability identification
PR.IP-12 - Security patch management
DE.CM-8 - Vulnerability scans
RS.MI-2 - Incident response and containment
🟡 ISO 27001:2022
A.12.6.1 - Management of technical vulnerabilities
A.14.2.1 - Secure development policy
A.12.3.1 - Configuration management
A.13.1.3 - Segregation of networks
A.12.2.1 - Change management
🟣 PCI DSS v4.0.1
Requirement 6.2 - Security patches for system components
Requirement 11.2 - Vulnerability scanning
Requirement 1.3 - Network segmentation