📄 Description (English)
An Unchecked Return Value vulnerability in the DNS module of Juniper Networks Junos OS on SRX Series allows an unauthenticated, network-based attacker to cause a Denial-of-Service (DoS).
If an SRX Series device configured for DNS processing, receives a specifically formatted DNS request flowd will crash and restart, which causes a service interruption until the process has recovered.
This issue affects Junos OS on SRX Series:
* 23.4 versions before 23.4R2-S5,
* 24.2 versions before 24.2R2-S1,
* 24.4 versions before 24.4R2.
This issue does not affect Junos OS versions before 23.4R1.
🤖 AI Executive Summary
A critical Denial-of-Service vulnerability exists in Juniper Networks Junos OS SRX Series DNS module (CVE-2026-21920) affecting versions 23.4 through 24.4. An unauthenticated attacker can crash the flowd process by sending a specially crafted DNS request, causing service interruption. This poses significant risk to Saudi organizations relying on SRX devices for network security and DNS filtering.
📄 Description (Arabic)
🤖 AI Intelligence Analysis Analyzed: May 4, 2026 00:55
🇸🇦 Saudi Arabia Impact Assessment
High impact on Saudi critical infrastructure sectors: (1) Banking & Financial Services (SAMA-regulated) — SRX devices commonly used for network perimeter security and DNS filtering in banking networks; (2) Government & Defense (NCA oversight) — widespread SRX deployment in government networks for DNS security; (3) Telecommunications (STC, Mobily, Zain) — SRX devices used in carrier networks for DNS traffic management; (4) Energy Sector (Saudi Aramco, SEC) — SRX deployment in SCADA/ICS network boundaries; (5) Healthcare — SRX devices protecting hospital networks and patient data. Unpatched devices are vulnerable to remote DoS attacks causing network service interruption.
🏢 Affected Saudi Sectors
Banking & Financial Services
Government & Defense
Telecommunications
Energy & Utilities
Healthcare
Critical Infrastructure
🎯 MITRE ATT&CK Techniques
⚖️ Saudi Risk Score (AI)
8.2
/ 10.0
🔧 Remediation Steps (English)
IMMEDIATE ACTIONS:
1. Identify all SRX Series devices running Junos OS versions 23.4 (before 23.4R2-S5), 24.2 (before 24.2R2-S1), or 24.4 (before 24.4R2)
2. Implement DNS request filtering at upstream devices to block malformed DNS packets
3. Enable DNS rate limiting and anomaly detection on SRX devices
4. Monitor flowd process stability and configure automatic restart notifications
PATCHING GUIDANCE:
1. Upgrade to patched versions: 23.4R2-S5 or later, 24.2R2-S1 or later, or 24.4R2 or later
2. Schedule maintenance windows for firmware updates during low-traffic periods
3. Test patches in lab environment before production deployment
4. Maintain backup configuration before upgrade
COMPENSATING CONTROLS (if immediate patching not possible):
1. Implement DNS proxy/filter at upstream network devices
2. Deploy IDS/IPS rules to detect and block malformed DNS requests
3. Configure DNS query logging and alerting for anomalies
4. Implement network segmentation to limit DNS traffic exposure
5. Enable syslog monitoring for flowd crash events
DETECTION RULES:
1. Monitor for flowd process restarts in Junos logs
2. Alert on DNS requests with unusual formatting or length
3. Track DNS query patterns for anomalies
4. Monitor system resource utilization spikes correlating with DNS traffic
🔧 خطوات المعالجة (العربية)
الإجراءات الفورية:
1. تحديد جميع أجهزة SRX التي تعمل بإصدارات Junos OS 23.4 (قبل 23.4R2-S5) أو 24.2 (قبل 24.2R2-S1) أو 24.4 (قبل 24.4R2)
2. تطبيق تصفية طلبات DNS على الأجهزة العلوية لحجب رسائل DNS المشوهة
3. تفعيل تحديد معدل DNS والكشف عن الشذوذ على أجهزة SRX
4. مراقبة استقرار عملية flowd وتكوين إشعارات إعادة التشغيل التلقائي
إرشادات التصحيح:
1. الترقية إلى الإصدارات المصححة: 23.4R2-S5 أو أحدث، 24.2R2-S1 أو أحدث، أو 24.4R2 أو أحدث
2. جدولة نوافذ الصيانة لتحديثات البرامج الثابتة خلال فترات حركة المرور المنخفضة
3. اختبار التصحيحات في بيئة المختبر قبل نشرها في الإنتاج
4. الاحتفاظ بنسخة احتياطية من الإعدادات قبل الترقية
الضوابط البديلة (إذا لم يكن التصحيح الفوري ممكناً):
1. تطبيق وكيل/مرشح DNS على أجهزة الشبكة العلوية
2. نشر قواعد IDS/IPS للكشف عن طلبات DNS المشوهة وحجبها
3. تكوين تسجيل استعلامات DNS والتنبيهات للشذوذ
4. تطبيق تقسيم الشبكة لتحديد تعرض حركة مرور DNS
5. تفعيل مراقبة syslog لأحداث توقف flowd
قواعد الكشف:
1. مراقبة إعادة تشغيل عملية flowd في سجلات Junos
2. التنبيه على طلبات DNS ذات التنسيق أو الطول غير المعتاد
3. تتبع أنماط استعلامات DNS للشذوذ
4. مراقبة ارتفاعات استخدام موارد النظام المرتبطة بحركة مرور DNS
📋 Regulatory Compliance Mapping
🟢 NCA ECC 2024
ECC 2024 A.12.6.1 — Management of technical vulnerabilities
ECC 2024 A.12.2.1 — Change management procedures
ECC 2024 A.14.2.1 — Security requirements analysis and specification
ECC 2024 A.16.1.5 — Response to information security incidents
🔵 SAMA CSF
ID.RA-1 — Asset management and vulnerability identification
PR.IP-12 — Security patch management
DE.CM-8 — Vulnerability scans and assessments
RS.RP-1 — Response planning and procedures
🟡 ISO 27001:2022
A.12.3.1 — Segregation of development, test and production environments
A.14.2.1 — Secure development policy
A.12.6.1 — Management of technical vulnerabilities
A.16.1.5 — Response to information security incidents
🟣 PCI DSS v4.0.1
Requirement 6.2 — Security patches and updates
Requirement 11.2 — Vulnerability scanning
Requirement 12.10 — Incident response procedures
📦 Affected Products / CPE 18 entries
juniper:junos:23.4
juniper:junos:23.4
juniper:junos:23.4
juniper:junos:23.4
juniper:junos:23.4
juniper:junos:23.4
juniper:junos:23.4
juniper:junos:23.4
juniper:junos:23.4
juniper:junos:24.2
juniper:junos:24.2
juniper:junos:24.2
juniper:junos:24.2
juniper:junos:24.2
juniper:junos:24.4
juniper:junos:24.4
juniper:junos:24.4
juniper:junos:24.4