📄 Description (English)
Exim Out-of-bounds Write Vulnerability — Exim contains an out-of-bounds write vulnerability which can allow for remote code execution.
🤖 AI Executive Summary
CVE-2019-16928 is a critical out-of-bounds write vulnerability in Exim mail transfer agent (MTA) that enables unauthenticated remote code execution. With a CVSS score of 9.0 and a confirmed public exploit, attackers can fully compromise mail servers without requiring any credentials. The vulnerability poses an immediate and severe threat to any organization running an unpatched Exim instance exposed to the internet. Given Exim's widespread deployment as a default MTA on many Linux distributions, the attack surface is substantial.
📄 Description (Arabic)
🤖 AI Intelligence Analysis Analyzed: Apr 14, 2026 21:49
🇸🇦 Saudi Arabia Impact Assessment
Saudi organizations across all sectors are at significant risk given Exim's prevalence on Linux-based mail infrastructure. Government entities under NCA oversight and SAMA-regulated financial institutions (banks, insurance companies) that operate internal or external mail servers using Exim are prime targets. Saudi Aramco and energy sector organizations with operational technology (OT) environments connected to IT mail infrastructure face potential lateral movement risks post-exploitation. Telecom providers such as STC and Zain KSA running large-scale mail relay infrastructure are also exposed. Healthcare organizations under MOH with limited patch management maturity are particularly vulnerable. Successful exploitation could lead to full server compromise, data exfiltration of sensitive communications, and use of compromised mail servers as pivot points for deeper network intrusion — a scenario of high concern given Saudi Arabia's elevated threat landscape from nation-state and cybercriminal actors.
🏢 Affected Saudi Sectors
Government
Banking
Energy
Telecom
Healthcare
Education
Defense
Retail
⚖️ Saudi Risk Score (AI)
9.2
/ 10.0
🔧 Remediation Steps (English)
IMMEDIATE ACTIONS (0-24 hours):
1. Identify all Exim instances across the environment using asset inventory or network scanning (nmap, Shodan internal queries).
2. Check Exim version: run 'exim --version' or 'exim4 --version' on all mail servers.
3. Isolate or firewall any Exim instances below version 4.92.2 from internet-facing exposure immediately.
4. Review mail server logs for anomalous SMTP connections, unusual process spawning, or unexpected outbound connections.
PATCHING GUIDANCE:
5. Upgrade Exim to version 4.92.2 or later immediately — this version contains the fix for CVE-2019-16928.
6. On Debian/Ubuntu: 'apt-get update && apt-get upgrade exim4'
7. On RHEL/CentOS: check vendor-specific backported patches via 'yum update exim'
8. Verify patch application by confirming version post-upgrade.
COMPENSATING CONTROLS (if patching is delayed):
9. Restrict SMTP access (port 25, 465, 587) to known trusted IP ranges using firewall ACLs.
10. Deploy an email security gateway or MTA proxy in front of vulnerable Exim instances.
11. Enable enhanced logging on SMTP sessions and forward to SIEM for anomaly detection.
12. Consider temporarily disabling Exim and routing mail through a patched relay.
DETECTION RULES:
13. SIEM rule: Alert on Exim process spawning unexpected child processes (e.g., /bin/sh, /bin/bash).
14. IDS/IPS: Deploy Snort/Suricata rules for CVE-2019-16928 exploit signatures.
15. Monitor for unusual files created in /tmp or /var/spool/exim directories.
16. Threat hunt for indicators of compromise: unexpected cron jobs, new user accounts, SSH authorized_keys modifications on mail servers.
🔧 خطوات المعالجة (العربية)
الإجراءات الفورية (خلال 0-24 ساعة):
1. تحديد جميع نسخ Exim في البيئة باستخدام جرد الأصول أو فحص الشبكة.
2. التحقق من إصدار Exim بتشغيل الأمر 'exim --version' على جميع خوادم البريد.
3. عزل أي نسخ Exim أقل من الإصدار 4.92.2 فوراً أو حمايتها بجدار الحماية.
4. مراجعة سجلات خادم البريد بحثاً عن اتصالات SMTP غير طبيعية أو عمليات غير متوقعة.
إرشادات التصحيح:
5. ترقية Exim إلى الإصدار 4.92.2 أو أحدث فوراً.
6. على Debian/Ubuntu: تشغيل 'apt-get update && apt-get upgrade exim4'
7. على RHEL/CentOS: التحقق من التصحيحات عبر 'yum update exim'
8. التحقق من تطبيق التصحيح بتأكيد الإصدار بعد الترقية.
ضوابط التعويض (في حال تأخر التصحيح):
9. تقييد الوصول إلى SMTP (المنافذ 25 و465 و587) على نطاقات IP موثوقة معروفة.
10. نشر بوابة أمان بريد إلكتروني أمام نسخ Exim الضعيفة.
11. تفعيل التسجيل المحسّن لجلسات SMTP وإرسالها إلى SIEM.
12. النظر في تعطيل Exim مؤقتاً وتوجيه البريد عبر مرحّل مُرقَّع.
قواعد الكشف:
13. قاعدة SIEM: تنبيه عند إنتاج عملية Exim لعمليات فرعية غير متوقعة.
14. IDS/IPS: نشر قواعد Snort/Suricata لتوقيعات استغلال CVE-2019-16928.
15. مراقبة الملفات غير المعتادة في مجلدات /tmp أو /var/spool/exim.
16. البحث عن مؤشرات الاختراق: مهام cron غير متوقعة، حسابات مستخدمين جديدة، تعديلات على SSH authorized_keys.
📋 Regulatory Compliance Mapping
🟢 NCA ECC 2024
ECC-1-4-2: Cybersecurity Vulnerability Management
ECC-1-3-2: Patch Management
ECC-2-2-1: Email Security Controls
ECC-1-5-1: Cybersecurity Incident Management
ECC-3-3-3: Server Hardening and Configuration Management
🔵 SAMA CSF
3.3.5 - Vulnerability Management
3.3.6 - Patch Management
3.2.5 - Email Security
3.3.9 - Penetration Testing and Red Teaming
3.4.2 - Cybersecurity Incident Management
🟡 ISO 27001:2022
A.12.6.1 - Management of Technical Vulnerabilities
A.14.2.2 - System Change Control Procedures
A.13.1.1 - Network Controls
A.16.1.1 - Responsibilities and Procedures for Incident Management
A.12.4.1 - Event Logging
🟣 PCI DSS v4.0
Requirement 6.3.3 - All system components are protected from known vulnerabilities by installing applicable security patches
Requirement 6.2.4 - Software engineering techniques to prevent common vulnerabilities
Requirement 11.3.1 - Internal vulnerability scans
Requirement 12.10.1 - Incident response plan
🔗 References & Sources 0
No references.
📦 Affected Products / CPE 1 entries
Exim:Exim Internet Mailer